1 Anthropologists as Scientists
Katie Nelson, Ph.D., Inver Hills Community College
Lara Braff, Ph.D., Grossmont College
Beth Shook, Ph.D., California State University, Chico
Kelsie Aguilera, M.A., University of Hawai‘i: Leeward Community College
This chapter is a section of a revision from “Chapter 1: Introduction to Biological Anthropology” by Katie Nelson, Lara Braff, Beth Shook, and Kelsie Aguilera. In Explorations: An Open Invitation to Biological Anthropology, first edition, edited by Beth Shook, Katie Nelson, Kelsie Aguilera, and Lara Braff, which is licensed under CC BY-NC 4.0.
Learning Objectives
- Explain key components of the scientific method.
- Differentiate between hypotheses, theories, and laws.
- Differentiate science from other ways of knowing.
Anthropologists as Scientists
Biological anthropologists use the scientific method as a way of learning about the world around them. Many people think of science as taking place in a sterile laboratory, but in biological anthropology it is just as likely to occur somewhere else, such as at a research station in Ethiopia, a field site in Tanzania, or a town in El Salvador. To understand how information in this field is established, it is important to recognize what science is and is not, as well as to understand how the scientific method actually works.
Recognizing Science
Science combines our natural curiosity with our ability to experiment so we can understand the world around us and address needs in our communities. Thanks to science, meteorologists can predict the weather, it takes a relatively small number of farmers to grow enough food to feed our large population, our medicine continues to improve, and over half of the world’s population owns a cell phone.
Anyone can participate in science—not just academics. In fact, children are often some of the best scientists (Figure 1.15). An early, well-known psychologist, Jean Piaget (1896–1980), argued that a child is a “little scientist,” internally motivated to experiment and explore their world. This can be seen when an infant repeatedly drops a toy to see if the parent will pick it up, or when a four-year-old sincerely asks “why” again and again. Maria Montessori (1870–1952), an Italian doctor and educator, was interested in how children learn. Through her research, she also recognized that children have natural scientific tendencies. Children have a desire to explore their environment, ask questions, use their imaginations, and learn by doing. In 1907, Montessori opened a school to foster children’s natural desire to learn this way. This developed a child-centered teaching method that has spread around the world and is being used in over 22,000 schools today. In anthropology and other scientific fields, the process of learning is more formalized, but scientists still benefit from the curiosity that motivates children and still experience the thrill of discovery.
Science represents both a body of knowledge and the process for learning that knowledge (the scientific method). Scientific claims can, at times, be difficult to distinguish from other information. Science also incorporates a broad range of methods to collect data, adding to the difficulty of knowing what science really is. This section will address four key characteristics that help us define and recognize science: (1) science studies the physical and natural world and how it works, (2) scientific explanations must be testable and refutable, (3) science relies on empirical (observable) evidence, and (4) science involves the scientific community.
Science Studies the Physical and Natural World and How It Works
Our physical and natural universe ranges from very small (e.g., electrons) to very large (e.g., Earth itself and the galaxies beyond it). Scientists often design their research to address how and why natural forces influence our physical and natural world. In biological anthropology, we focus our questions on humans as well as other primate species, both living and extinct. We ask questions like: What influences a primate’s diet? Why do humans walk on two legs? And did Neanderthals and modern humans interbreed?
There are very few questions that are considered off-limits in science. That being said, the scope of scientific investigation is generally focused on natural phenomena and natural processes and excludes the supernatural. People often regard the supernatural, whether it be a ghost, luck, or god, as working outside the laws of the universe, which makes it difficult to study with a scientific approach. Science neither supports nor contradicts the existence of supernatural powers—it simply does not include the supernatural in its explanations.
Scientific Explanations Must Be Testable and Refutable
The goal of scientists is to identify a research question and then identify the best answer(s) to that question. For example, an excavation of a cemetery may reveal that many people buried there had unhealed fractures when they died, leading the anthropologist to ask: “Why did this population experience more broken bones than their neighbors?” There might be multiple explanations to address this question, such as a lack of calcium in their diets, participation in dangerous work, or violent conflict with neighbors; these explanations are considered hypotheses. In the past, you might have learned that a hypothesis is an “educated guess,” but in science, hypotheses are much more than that. A scientific hypothesis reflects a scientist’s knowledge-based experiences and background research. A hypothesis is better defined as an explanation of observed facts; hypotheses explain how and why observed phenomena are the way they are.
Scientific hypotheses should generate expectations that are testable. For example, if the best explanation regarding our cemetery population was that they were experiencing violent conflict with their neighbors, we should expect to find clues, like weapons or protective walls around their homes, in the anthropological record to support this. Alternatively, if this population did not experience violent conflict with their neighbors, we may eventually be able to gather enough evidence to rule out (refute) this explanation. An important part of science is rigorous testing. Science does not prove any hypothesis. However, a strong hypothesis is one that has strong supporting evidence and has not yet been disproven.
Science Relies on Empirical Evidence
The word empirical refers to experience that is verified by observation (rather than evidence that derives primarily from logic or theory). In anthropology, much evidence about our world is collected by observation through fieldwork or in a laboratory. The most reliable studies are based on accurately and precisely recorded observations. Scientists value studies that explain exactly what methods were used so that their data collection and analysis processes are reproducible. This allows for other scientists to expand the study or provide new insights into the observations.
Science Involves the Scientific Community
Contrary to many Hollywood science fiction films, good science is not carried out in isolation in a secret basement laboratory; rather, it is done as part of a community. Scientists pay attention to what others have done before them, present new ideas to each other, and publish in scientific journals. Most scientific research is collaborative, bringing together researchers with different types of specialized knowledge to work on a shared project. Today, thanks to technology, scientific projects can bring together researchers from different backgrounds, experiences, locations, and perspectives. Most big anthropological questions such as “Where did modern humans develop?,” “What genetic changes make us uniquely human?,” and “How did cooperative behavior evolve?” cannot be addressed with one simple study but are tested with different lines of evidence and by different scientists over time.
Working within a scientific community supports one of the most valuable aspects of science: that science is self-correcting. Science that is openly communicated with others allows for a system with checks and balances: competing explanations can be proposed and questionable studies can be reevaluated. Ultimately, the goal is that through science the best explanations will stand the test of time.
How Science Works: The Scientific Method
Most students have learned the scientific method as a simple linear, or perhaps circular, process (see, e.g., Figure 1.16). Typically, the process is said to begin with making observations about the natural world. This leads to the development of a scientific hypothesis. From the hypothesis a set of predictions can be made, which are then tested by experimentation or by making additional observations. Scientific predictions are often phrased as “if… then…” statements, such as “If hypothesis A is true, then this experiment will show outcome B.” The results of a scientific study should then either support or reject the hypothesis.
This simple version of the scientific method is valuable because it highlights the key aspects that should be present in any scientific research experiment or scientific paper. However, this simplistic view does not accurately represent the dynamic and creative side of science, nor does it identify the complex steps that are incorporated into a scientist’s routine.
Figure 1.17 provides an alternative representation of the scientific method that emphasizes the many paths to scientific discovery. While still incorporating the key components of making observations, testing ideas, and interpreting results, this chart shows that scientific ideas have many possible starting points and influences, and scientists often repeat steps and circle back around. Gathering evidence does not always rest on experiments in the laboratory. Evaluating data is not always clear-cut, and results are sometimes surprising or inconclusive. Many important discoveries were in fact made by mistake. For example, engineer Percy Spencer accidentally melted a chocolate bar in his pocket with a magnetron, which became the first microwave, and Spencer Silver invented the adhesive for 3M Post-it ® notes while trying to develop a strong glue. The real scientific process is more similar to the philosophy of the animated television character Ms. Frizzle from The Magic School Bus, “Take chances, make mistakes, get messy.”
Two key components lacking in the simple version of the scientific method are exploration and discovery. There are many reasons that a scientist might choose a particular research question: they may be motivated by personal experience, struck by something they read, or inspired by a student’s question in class. Often scientific research reveals more questions than answers, so experienced researchers rarely lack problems to solve. But identifying a research question is just part of the process; most scientists spend more time exploring the literature, sharing ideas, asking questions, and planning their research project than conducting the test itself.
Science itself is a social enterprise that is influenced by cultural issues and values, as well as funding priorities. For example, corporations are the biggest funders of scientific research, followed by government agencies such as the National Science Foundation (which also fund many research projects done at colleges and universities). Those organizations have great influence on what is considered valuable research at any given time. For example, the World Health Organization (WHO) has classified many diseases as “neglected tropical diseases,” including dengue, leprosy, rabies, and hookworm. Together these diseases affect an estimated one billion people, mostly in impoverished areas. While these debilitating tropical diseases can be as deadly as diseases that receive more attention, like AIDS and tuberculosis, they receive comparatively little funding due to political priorities (Farmer et al. 2013).
Also important to the scientific process are interactions within the scientific community. Scientific collaboration can take place through informal discussion over a cup of coffee as well as more formal interactions, such as presenting at conferences and engaging in scholarly peer review. Scholarly peer review describes the process whereby an author’s work must pass the scrutiny of other experts in the field before being accepted for publication in a journal or book. This helps keep scientists accountable for ethically responsible research projects and papers. Additionally, presenting data at conferences and in articles and books allows researchers to receive critical feedback from academic peers and others to test these ideas and further the field of science toward identifying the best explanations. It is important that the scientific field include researchers with diverse identities, backgrounds, and experiences so that researchers ask new questions, innovate, and problem solve more effectively.
Hypotheses, Theories, and Laws
Scientific investigation occurs at many levels, from investigating individual cases (e.g., “What is causing this child’s mysterious illness?”) to understanding processes that affect most of us (“What is the ideal amount of sleep for an adult?”). All of these questions are important and will generate different types of testable scientific explanations. So far, we have used the term hypothesis to describe these scientific ideas about why observed phenomena are the way they are. Hypotheses are typically explanations that address a narrow set of phenomena, such as (in anthropology) a particular human population or primate species.
In science, a theory is an explanation of observations that addresses a wide range of phenomena. Like hypotheses, theories also explain how or why something occurs, rely on empirical evidence, and are testable and able to be refuted. Because the term theory is often used casually outside of science, you may hear people try to dismiss a scientific claim as “just a theory.” In science there are often multiple competing theories, but over time some are eliminated, leaving standing the theory or theories that best explain the most evidence. Scientific theories that have stood the test of time are thus supported by many lines of evidence and are usually reliable. Some well-tested theories accepted by most scientists include the theory of general relativity, which explains the law of gravitation and its relation to other forces, and evolutionary theory, which describes how heritable traits can change in a population over time.
While scientific hypotheses and theories share many characteristics, laws are quite different. A law is a prediction about what will happen given certain conditions, not an explanation for how or why it happens. A law is not a “mature” version of a theory. For example, Newton’s universal law of gravity allows us to predict the gravitational force (F) between any two objects using the equation F=G(m1m2)/r2, but it does not explain why gravity works. Laws are often mathematical, and some well-known laws include Newton’s three laws of motion and Mendel’s laws of genetic inheritance. Laws are important, and their discovery often promotes the development of theories.
To demonstrate how important laws can be—and to show how unusual things can inspire scientific discoveries—we can use the story of the ancient Greek mathematician and inventor Archimedes (Figure 1.18). Archimedes’s buoyancy principle is a law that is useful for many things, including density calculations and designing ships. Purportedly, he made this discovery when he noticed the water level rise in the bathtub when he climbed in it. Realizing its importance, he is said to have shouted “Eureka” and proceeded to run naked through the city of Syracuse. While this fun story may or may not be true, it does remain that scientific laws, alongside scientific hypotheses and theories, have a very important role in the scientific process and in generating scientific explanations about our natural world.
Ways of Knowing: Science, Faith, and Anthropology
In anthropology, we recognize that there are many ways of knowing things. For instance, you might know that fingernails are softer than metal because as a child you accidentally stapled through your fingernail while doing an art project (a coauthor of this textbook once experienced this). This would be an example of knowledge you gained through experience. You might also know that inserting a knife into an electrical outlet is dangerous and could greatly harm you. Hopefully you learned this not from personal experience but through instruction from parents, teachers, and others in your social group. The degree to which humans rely on and benefit from the experiential knowledge of others is an important characteristic of what makes us human.
A unified way of knowing that is shared by a group of people and used to explain and predict phenomena is called a knowledge system. Human knowledge systems are diverse and reflect the wide range of cultures and societies throughout the world and through time.
Science and religion are both knowledge systems. Yet they differ in important ways. The type of knowledge gained from science is often called scientific understanding. As we have explored in the previous section, scientific understanding can change and relies on evidence and rigorous, repeated testing. Religious or spiritual ways of knowing are called belief, which is different from scientific understanding because they do not require repeated testing or validation (although they can rely on observations and experiences). Instead, belief relies on trust and faith.
Different individuals, cultures, and societies may place more value on one type of knowing than another, although most use a combination that includes science, empiricism, and religion. In fact, Bronisław Malinowski (1884–1942), an important anthropologist of the early twentieth century, concluded that all societies use both religion and science in some way or another, because they are both common ways that humans experience the world.
In contemporary societies such as the United States, science and (some) religions conflict on the topic of human origins. Nearly every culture and society has a unique origin story that explains where they came from and how they came to be who they are today. These stories are often integrated into the culture’s religious belief system. Many anthropologists are interested in faith-based origin stories and other beliefs because they show us how a particular group of people explain the world and their place in it. Anthropologists also value scientific understanding as the basis for how humans vary biologically and change over time. In other words, anthropologists value the multiple knowledge systems of different groups and use them to understand the human condition in a broad and inclusive way.
It is also important to note that scientists often depend on the local knowledge of the people with whom they work to understand elements of the natural or physical world that science has not yet investigated. Many groups, including Indigenous peoples, know about the world through prolonged relationships with the environment. Indigenous knowledge systems—specific to an Indigenous community or group—are informed by their own empirical observation of a specific environment and passed down over generations.
While religion and Indigenous knowledge systems may play a complementary role in helping anthropologists understand the human condition, they are distinct from science. The anthropological subdiscipline of biological anthropology is based on scientific ways of knowing about humans and human origins. In this volume, we will exclusively explore what science tells us about how humans came to be and why we are the way we are today. Therefore, you do not need to believe in evolution to master this material, because belief is not a scientific way of knowing. For this textbook, you only need to understand the scientific perspectives of evolution.
Throughout our lives, each of us work to reconcile our worldview with the different ways we have of knowing things. This is part of our lifelong intellectual journey. It is also, in our opinion, one of the most exciting parts of learning. We are pleased you have joined us on this journey of knowledge about humanity and yourself!
Summary
Biological anthropology relies on the scientific method to investigate humans and other primates across time and place. While research in this field begins with careful observation, hypotheses are more closely examined with empirical evidence from excavation, fieldwork, or laboratory study. Focusing on this scientific foundation, the discipline allows anthropologists to move beyond belief and speculation to produce knowledge that is testable and continually open to challenge.
Findings are continually debated, reviewed, and revised, ensuring that explanations improve and remain grounded in current and relevant evidence. If you have not caught on already, this textbook follows the same process, reflecting the evolving body of knowledge that is biological anthropology.
Review Questions
- What is science?
- What is the scientific method?
- How does science compare to other ways of knowing?
Key Terms
Empirical: Evidence that is verifiable by observation or experience instead of relying primarily on logic or theory.
Faith: Complete trust or confidence in the doctrines of a religion, typically based on spiritual apprehension rather than empirical proof.
Knowledge system: A unified way of knowing that is shared by a group of people and used to explain and predict phenomena.
Participant observation: A research method common in cultural anthropology that involves living with, observing, and participating in the same activities as the people one studies.
Scholarly peer review: The process whereby an author’s work must pass the scrutiny of other experts in the field before being published in a journal or book.
Scientific understanding: Knowledge accumulated by systematic scientific study, supported by rigorous testing and organized by general principles.
Theory: An explanation of observations that typically addresses a wide range of phenomena.
For Further Exploration
Understanding Science website (a project of the University of California Museum of Paleontology.
Anticole, Matt. n.d. “What’s the Difference between a Scientific Law and Theory?” TedEd Lesson. Accessed January 28, 2023. 28, 2023.
Chan, Keith. 2021. “Icebreaker Science.” In Explorations: Lab and Activities Manual, edited by Beth Shook, Katie Nelson, Kelsie Aguilera, and Lara Braff. Arlington, VA: American Anthropological Association.
Chizmeshya, Sydney Quinn, and Katherine E. Brent. 2021. “Knowing and Believing.” In Explorations: Lab and Activities Manual, edited by Beth Shook, Katie Nelson, Kelsie Aguilera, and Lara Braff. Arlington, VA: American Anthropological Association.
Pfister, Anne E. 2021. “Science and Belief: Just Because We Can, Doesn’t Always Mean We Should.” In Explorations: Lab and Activities Manual edited by Beth Shook, Katie Nelson, Kelsie Aguilera, and Lara Braff. Arlington, VA: American Anthropological Association.
References
Binford, Leigh. 2016. The El Mozote Massacre: Human Rights and Global Implications. Revised and expanded edition. Tucson: University of Arizona Press.
Estrada, Alejandro, Paul A. Garber, Anthony B. Rylands, Christian Roos, Eduardo Fernandez-Duque, Anthony Di Fiore, K. Anne-Isola Nekaris, et al. 2017. “Impending Extinction Crisis of the World’s Primates: Why Primates Matter.” Science Advances 3(229): 1–16.
Farmer, Paul. 2006. AIDS and Accusation: Haiti and the Geography of Blame. Berkeley: University of California Press.
Farmer, Paul, Matthew Basilico, Vanessa Kerry, Madeleine Ballard, Anne Becker, Gene Bukhman, Ophelia Dahl, et al. 2013. “Global Health Priorities for the Early Twenty-first Century.” In Reimagining Global Health: An Introduction, edited by Paul Farmer, Jim Yong Kim, Arthur Kleinman, and Matthew Basilico, 302–339. Berkeley: University of California Press.
Kenyon, Kathleen. 1979. Archaeology in the Holy Land. New York: W.W. Norton.
Malotki, Ekkehart. 1983. Hopi Time: A Linguistic Analysis of the Temporal Concepts in the Hopi Language. Berlin: De Gruyter.
Mead, Margaret. 1928. Coming of Age in Samoa. Oxford: Morrow.
Ochs, Elinor and Bambi Schieffelin. 2017. “Language Socialization: An Historical Overview.” In Encyclopedia of Language and Education, Volume 8, edited by Patricia Duff, 3-16. New York: Springer.
Rathje, William and Cullen Murphy. 1992. “Five Major Myths about Garbage, and Why They’re Wrong.” Smithsonian 23, no. 4: 113-122.
TANN. 2018. “Mexican Anthropologists Put Face on Nearly 14,000-Year-Old Woman.” Archaeology News Network, August 19, 2018. Accessed on November 16, 2022.
Whorf, Benjamin. 1956. Language, Thought, and Reality. Cambridge: MIT Press.
Michael B. C. Rivera, Ph.D., University of Cambridge
This chapter is a revision from "Chapter 13: Race and Human Variation” by Michael B. C. Rivera. In Explorations: An Open Invitation to Biological Anthropology, first edition, edited by Beth Shook, Katie Nelson, Kelsie Aguilera, and Lara Braff, which is licensed under CC BY-NC 4.0.
Learning Objectives
- Illustrate the troubling history of “race” concepts.
- Explain human variation and evolution as the thematic roots of biological anthropology as a discipline.
- Critique earlier “race” concepts based on a contemporary understanding of the apportionment of human genetic variation.
- Explain how biological variation in humans is distributed clinally and in accordance with both isolation-by-distance and Out-of-Africa models.
- Identify phenotypic traits that reflect selective and neutral evolution.
- Extend this more-nuanced view of human variation to today’s research, the implications for biomedical studies, applications in forensic anthropology, and other social/cultural/political concerns.
Humans exhibit biological variation. Humans also have a universal desire to categorize other humans in order to make sense of the world around them. Since the birth of the discipline of biological anthropology, we have been interested in studying how humans vary biologically and what the sources of this variation are. Before we tackle these big problems, first consider this question: Why should we study human variation?
There are certainly academic reasons for studying human variation. First, it is highly interesting and important to consider the evolution of our species (see Chapters 9–12) and how our biological variation may be similar to (or different from) that of other species (e.g., other primates and apes; see Chapters 5 and 6). Second, anthropologists study modern human variation to understand how different biological traits developed over evolutionary time (see Figure 14.1). Suppose we are able to grasp the evolutionary processes that produce the differences in biology, physiology, body chemistry, behavior, and culture (human variation). In that case, we can make more accurate inferences about evolution and adaptation among our hominin ancestors, complementing our study of fossil evidence and the archaeological record. Third, as will be discussed in more detail later on, it is important to consider that biological variation among humans has biomedical, forensic, and sociopolitical implications. For these reasons, the study of human variation and evolution has formed the basis of anthropological inquiry for centuries and continues to be a major source of intrigue and inspiration for scientific research conducted today.
An even-more-important role of the biological anthropologist is to improve public understanding of human evolution and variation—outside of academic circles. Terms such as race and ethnicity are used in everyday conversations and in formal settings within and outside academia. The division of humankind into smaller, discrete categories is a regular occurrence in day-to-day life. This can be seen regularly when governments acquire census data with a heading like “geographic origin” or “ethnicity.” Furthermore, such checkboxes and drop-down lists are commonly seen as part of the identifying information required for surveys and job applications.
According to professors of anthropology, ethnic studies, and sociology, race is often understood as rooted in biological differences, ranging from such familiar traits as skin color or eye shape to variations at the genetic level. However, race can also be studied as an “ideological construct” that goes beyond biological and genetic bases (Fuentes et al. 2019), at different times relating to our ethnicities, languages, religious beliefs, and cultural practices. Sometimes people associate racial identity with the concept of socioeconomic status or position, or they link ideas about race to what passport someone has, how long they have been in a country, or how well they have “integrated” into a population.
Some of these ideas about ethnicity have huge social and political impacts, and notions of race have been part of the motivation behind various forms of racism and prejudice today, as well as many wars and genocides throughout history. Racism manifests in many ways—from instances of bullying between kids on school playgrounds to underpaid minorities in the workforce, and from verbal abuse hurled at people of color to violent physical behaviors against those of a certain race. Prejudice can be characterized as negative views toward another group based on some perceived characteristic that makes all members of that group worthy of disdain, disrespect, or exclusion (not solely along racial lines but also according to [dis]ability, gender, sexual orientation, or socioeconomic background, for example). According to Shay-Akil McLean (2014), “Racism is not something particular to the United States and race is not the same everywhere in the world. Racial categories serve particular contextual purposes depending on the society they are used in, but generally follow the base logic of the supremacy of one type of human body over all others (ordering these human bodies in a hierarchical fashion).” Choosing which biological or nonbiological features to use when discussing race is always a social process (Omi and Winant 2014). Race concepts have no validity to them unless people continue to use them in their daily lives—and, in the worst cases, to use them to justify racist behaviors and problematic ideas about racial difference or superiority/inferiority. Recent work in anthropological genetics has revealed the similarities amongst humans on a molecular level and the relatively few differences that exist between populations (Omi and Winant 2014).
The role of the biological anthropologist becomes crucial in the public sphere, because we may be able to debunk myths surrounding human variation and shed light, for the nonanthropologists around us, on how human variation is actually distributed worldwide (see Figure 14.1). Rooted in scientific observations, our work can help nonanthropologists recognize how common ideas about “race” often have no biological or genetic basis. Many anthropologists work hard to educate students on the history of where race concepts come from, why and how they last in public consciousness, and how we become more conscious of racial issues and the need to fight against racism in our societies. Throughout this chapter, I will highlight how humans cannot actually be divided into discrete “races,” because most traits vary on a continuous basis and human biology is, in fact, very homogenous compared to the greater genetic variation we observe in closely related species. Molecular anthropology, or anthropological genetics, continues to add new layers to our understanding of human biological variation and the evolutionary processes that gave rise to the contemporary patterns of human variation. The study of human variation has not always been unbiased, and thinkers and scientists have always worked in their particular sociohistorical context. For this reason, this chapter opens with a brief overview of race concepts throughout history, many of which relied on unethical and unscientific notions about different human groups.
Special Topic: My Experiences as an Asian Academic
My name is Michael, and I am a biological anthropologist and archaeologist (Figure 14.2). What strikes me as most interesting to investigate is human biological variation today and the study of past human evolution. For instance, some of my research on ancient coastal populations has revealed positive effects of coastal living on dietary health and many unique adaptations in bones and teeth when living near rivers and beaches. I love talking to students and nonscientists about bioanthropologists’ work, through teaching, science communication events, and writing book chapters like this one. I grew up in Hong Kong, a city in southern China. My father is from the Philippines and my mother is from Hong Kong, which makes me a mixed Filipino-Chinese academic. Growing up, I noticed that people came in all shapes, sizes, and colors. My life is very different now in that I have gained the expertise to explain those differences, and I feel a great responsibility to guide those new to anthropology toward their own understandings of diversity.
Biological anthropology is not taught extensively in Hong Kong, so I moved to the United Kingdom to earn my bachelor’s, master’s, and doctorate degrees. It was fascinating to me that we could answer important questions about human variation and history using scientific methods. However, I did not have many minority academic role models to look up to while I was at university. My department was made up almost exclusively of white westerner faculty, and it was hard to imagine I could one day get a job at these western institutions. While pursuing my degrees, I also remember several instances of my research contributions being overlooked or dismissed. Sometimes professors and fellow students would make racist comments toward Asian scholars (including me) and other Black, Indigenous and researchers of color, making us greatly uncomfortable in those spaces. When one of us would work up the courage to tell university leaders our experiences of being stereotyped, dismissed, or insulted, we received little support and were further excluded from research and teaching activities. This is a common experience for Black, Indigenous, and other people of color who pursue biological anthropology, and we face the difficult choice between leaving the field or bearing with such unsafe spaces.
It became important to me at that time to find other academics of color with whom to share experiences and form community. I feel inspired by all my colleagues who advocate for greater representation and diversity in universities (whether they are minority academics or not). I admire many of my fellow researchers who are underrepresented and do a great job of representing minority groups through their cutting-edge research and quality teaching at the undergraduate and graduate levels. Although I no longer work in the West, it has remained my great hope that those in the West and the “Global North” will continue to improve university culture, and I support any efforts there to welcome all scholars.
My current work is based in Hong Kong, where I am deeply dedicated to helping develop biological anthropology in East and Southeast Asia and promoting research from our home regions on the international scene. The study of anthropology really highlights how we share a common humanity and history. Being somebody who is “mixed race” and Asian likely played a key role in steering me toward the study of human variation. As this chapter hopefully shows, there is a lot to discuss about race and ethnicity regarding the discipline’s history and current understandings of human diversity. Some scientific and technological advancements today are misused for reasons to do with money, politics, or the continuation of antiquated ideas. It is my belief, alongside many of my friends and fellow anthropologists, that science should be more about empathy toward all members of our species and contributing to the intellectual and technological nourishment of society. After speaking to many members of the public, as well as my own undergraduate students, I have received lovely messages from other individuals of color expressing thanks and appreciation for my presence and understanding as a minority scientist and mentor figure. Anthropology needs much more diversity as well as to make room for those who have traveled different routes into the discipline. All paths taken into anthropology are valid and valuable. I would encourage everyone to study anthropology—it is a field for understanding and celebrating the intricacies of human diversity.
The History of "Race" Concepts
“Race” in the Classical Era
The earliest classification systems used to understand human variation are evidenced by ancient manuscripts, scrolls, and stone tablets recovered through archaeological, historical, and literary research. The Ancient Egyptians had the Book of Gates, dated to the New Kingdom between 1550 B.C.E. and 1077 B.C.E (Figure 14.3). In one part of this tome dedicated to depictions of the underworld, scribes used pictures and hieroglyphics to illustrate a division of Egyptian people into the four categories known to them at the time: the Aamu (Asiatics), the Nehesu (Nubians), the Reth (Egyptians), and the Themehu (Libyans). Though not rooted in any scientific basis like our current understandings of human variation today, the Ancient Egyptians believed that each of these groups were made of a distinctive category of people, distinguishable by their skin color, place of origin, and even behavioral traits.
Another well-known early document is the Bible, where it is written that all humankind descends from one of three sons of Noah: Shem (the ancestor to all olive-skinned Asians), Japheth (the ancestor to pale-skinned Europeans), and Ham (the ancestor to darker-skinned Africans). Similar to the Ancient Egyptians, these distinctions were based on behavioral traits and skin color. More recent work in historiography and linguistics suggest that the branches of “Hamites,” “Japhethites,” and “Shemites” may also relate to the formation of three independent language groups some time between 1000 and 3000 B.C.E. With the continued proliferation of Christianity, this concept of approximately three racial groupings lasted until the Middle Ages and spread as far across Eurasia as crusaders and missionaries ventured at the time.
There is also the “Great Chain of Being,” conceived by ancient Greek philosophers like Plato (427‒348 B.C.E.) and Aristotle (384‒322 B.C.E.). They played a key role in laying the foundations of empirical science, whereby observations of everything from animals to humans were noted with the aim of creating taxonomic categories. Aristotle describes the Great Chain of Being as a ladder along which all objects, plants, animals, humans, and celestial bodies can be mapped in an overall hierarchy (in the order of existential importance, with humans placed near the top, just beneath divine beings; see Figure 14.4). When he writes about humans, Aristotle expressed the belief that certain people are inherently (or genetically) more instinctive rulers, while others are more natural fits for the life of a worker or enslaved person. Based on research by biological anthropologists, we currently recognize that these early systems of classification and hierarchization are unhelpful in studying human biological variation. Both behavioral traits and physical traits are coded for by multiple genes each, and how we exhibit those traits based on our genetics can vary significantly even between individuals of the same population.
“Race” during the Scientific Revolution
The 1400s to 1600s saw the beginnings of the Scientific Revolution in Western societies, with thinkers like Nicholas Copernicus, Galileo Galilei, and Leonardo Da Vinci publishing some of their most important findings. While by no means the first or only scholars globally to use observation and experimentation to understand the world around them, early scientists living at the end of the medieval period in Europe increasingly employed more experimentation, quantification, and rational thought in their work. This is the main difference between the work of the ancient Egyptians, Romans, and Greeks and that of later scientists such as Isaac Newton and Carl Linnaeus in the 1600s and 1700s.
Linnaeus is the author of Systema Naturae (1758), in which he classified all plants and animals under the formalized naming system known as binomial nomenclature (Figure 14.5). This system is typological, in that organisms are placed into groups according to how they are similar or different to others under study. What was most anthropologically notable about Linnaeus’s typological system was that he was one of the first to group humans with apes and monkeys, based on the anatomical similarities between humans and nonhuman primates. However, Linnaeus viewed the world in line with essentialism, a problematic concept that dictates that there are a unique set of characteristics that organisms of a specific kind must have and that would remove organisms from taxonomic categorizations if they lacked any of the required criteria.
Linnaeus subdivided the human species into four varieties, with overtly racist categories based on skin color and “inherent” behaviors. Some European scientists during this period were not aware of their own biases skewing their interpretations of biological variation, while others deliberately worked to shape public perceptions of human variation in ways that established “otherness” and enforced European domination and the subordination of non-European people. The conclusions and claims at which they arrived, consciously or subconsciously, often fit the times they were living through—the so-called Age of Discovery, when the superiority of European cultures over others was a pervasive idea throughout people’s social and political lives. Although much of Eurasia was linked by spice- and silk-trading routes, the European colonial period between the 1400s and 1700s was marked by many new and unfortunately violent encounters overseas (Figure 14.6). When Europeans arrived by ship on the shores of continents that were already inhabited, it was their first meeting with the Indigenous peoples of the Americas and Australasia, who looked, spoke, and behaved differently from peoples with whom they were familiar. Building on the idea of species and “subspecies,” natural historians of this time invented the term race, from the French rasse meaning “local strain.”
Another scientist of the times, Johann Friedrich Blumenbach (1752‒1840), classified humans into five races based on his observations of cranial form variation as well as skin color. He thus dubbed the “original” form of the human cranium the “Caucasian” form, with the idea that the ideal climate conditions for early humans would have been in the Caucasus region near the Caspian Sea. The key insight Blumenbach presented was that human variation in any particular trait should be more accurately viewed as falling along a gradation (Figure 14.7). While some of his theories were correct according to what we observe today with more knowledge in genetics, they erroneously believed that human “subspecies” were “degenerated” or “transformed” varieties of an ancestral Caucasian or European race. According to them, the Caucasian cranial dimensions were the least changed over human evolutionary time, while the other skull forms represented geographic variants of this “original.” As will be discussed in greater detail later in this chapter, we have genetic and craniometric evidence for sub-Saharan Africa being the origin of the human species instead (see Chapter 12 on the fossil record that places the origins of modern Homo sapiens in north and east Africa). Based on work that shows how most biological characteristics are coded for by nonassociated genes, it is not reasonable to draw links between individuals’ personalities and their skull shapes.
“Race” and the Dawn of Scientific Racism
Between the 1800s and mid-1900s, and contrary to what you might expect, an increased use of scientific methods to justify racial schemes developed in scholarship. Differing from earlier views, which saw all humans as environmentally deviated from one “original” humankind, classification systems after 1800 became more polygenetic (viewing all people as having separate origins) rather than monogenetic (viewing all people as having a single origin). Instead of moving closer to our modern-day understandings of human variation, there was increased support for the notion that each race was created separately and with different attributes (intelligence, temperament, and appearance).
The 1800s were an important precursor to modern biological anthropology as we know it, given that this was when the scientific measurement of human physical features (anthropometry) truly became popularized. However, empirical studies in the 1800s pushed even further the idea that Europeans were culturally and biologically superior to others. While considered one of the pioneers of American “physical” anthropology, Samuel George Morton (1799‒1851) was a scholar who had a large role in perpetuating 1800s scientific racism. By measuring cranial size and shape, he calculated that “Caucasians,” on average, have greater cranial volumes than other groups, such as the Indigenous peoples of the Americas and peoples Morton referred to collectively as “Negros.” Today, we know that cranial size variation depends on such factors as Allen’s and Bergmann’s rules, which give a more likely explanation: in colder environments, it is advantageous for those living there to have larger and rounder heads because they conserve heat more effectively than more slender heads (Beals et al. 1984). The leading figures in craniometry during the 1800s instead were linked heavily with powerful individuals and wealthy sociopolitical institutions and financial bodies. Theories in support of hierarchical racial schemes using “scientific” bases certainly helped continue the exploitative and unethical trafficking and enslavement of Africans between the 1500s and 1800s.
Morton went on to write in his publication Crania Americana (1839) a number of views that fit with a concept called biological determinism. The idea behind biological determinism is that an association exists between people’s physical characteristics and their behavior, intelligence, ability, values, and morals. If the idea is that some groups of people are essentially superior to others in cognitive ability and temperament, then it is easier to justify the unequal treatment of certain groups based on outward appearances. Another such problematic thinker was Paul Broca (1824‒1880), after whom a region of the frontal lobe related to language use is named (Broca’s area). Influenced by Morton, Broca likewise claimed that internal skull capacities could be linked with skin color and cognitive ability. He went on to justify the European colonization of other global territories by purporting it was noble for a biologically more “civilized” population to improve the “humanity” of more “barbaric” populations. Today, these theories of Morton, Broca, and others like them are known to have no scientific basis. If we could speak with them today, they would likely try to emphasize that their conclusions were based on empirical evidence and not a priori reasoning. However, we now can clearly see that their reasoning was biased and affected by prevailing societal views at the time.
“Race” and the Beginnings of Physical Anthropology
In the early 20th century, we saw a number of new figures coming into the science of human variation and shifting the theoretical focus within. Most notably, these included Aleš Hrdlička and Franz Boas.
Aleš Hrdlička (1869‒1943) was a Czech anthropologist who moved to the United States. In 1903, he established the physical anthropology section of the National Museum of Natural History (Figure 14.8). In 1918, he founded the American Journal of Physical Anthropology, which remains one of the foremost scientific journals disseminating bioanthropological research. As part of his work and the scope of the journal, he differentiated “physical anthropology” from other kinds of anthropology: he wrote that physical anthropology is “the study of racial anatomy, physiology, and pathology” and “the study of man’s variation” (Hrdlička 1918). In some ways, although the scope and technological capabilities of biological anthropologists have changed significantly, Hrdlička established an area of inquiry that has continued and prospered for over a hundred years.
Franz Boas (1858‒1942) was a German American anthropologist who established the four-field anthropology system in the United States and founded the American Anthropological Association in 1902. He argued that the scientific method should be used in the study of human cultures and the comparative method for looking at human biology worldwide. One of Boas’s significant contributions to biological anthropology was the study of skull dimensions with respect to race. After a long-term research project, he demonstrated how cranial form was highly dependent on cultural and environmental factors and that human behaviors were influenced primarily not by genes but by social learning. He wrote in one essay for the journal Science: “While individuals differ, biological differences between races are small. There is no reason to believe that one race is by nature so much more intelligent, endowed with great willpower, or emotionally more stable than another, that the difference would materially influence its culture” (Boas 1931:6). This conclusion directly contrasted with the theories of the past that relied on biological determinism. Biological anthropologists today have found evidence that corroborates Boas’s explanations: societies do not exist on a hierarchy or gradation of “civilizedness” but instead are shaped by the world around them, their demographic histories, and the interactions they have with other groups.
The first half of the 1900s still involved some research that was essentialist and focused on proving racial determinism. Anthropologists like Francis Galton (1822‒1911) and Earnest A. Hooton (1887‒1954) created the field of eugenics as an attempt to formalize the social scientific study of “fitness” and “superiority” among members of 19th-century Europe. As a way of “dealing with” criminals, diseased individuals, and “uncivilized” people, eugenicists recommended prohibiting parts of the population from being married or sterilizing these members of society so they could no longer procreate (Figure 14.9). They instead encouraged “reproduction in individual families with sound physiques, good mental endowments, and demonstrable social and economic capability” (Hooton 1936). In the 1930s, Nazi Germany used this false idea of there being “pure races” to highly destructive effect. The need to be protected against admixture from “unfit” groups was their justification for their blatant racism and purging of citizens that fell under their subjective criteria.
It should be noted that eugenicist ideas were popularly discussed and debated in many non-European contexts, as in the U.S., China, and South Africa, too. The Immigration Restriction Act of 1924 was passed in the United States, with the explicit aim of reducing the country’s “burden” of people considered inferior by restricting immigration of eastern European Jews, Italians, Africans, Arabs, and Asians. In the early 1900s, Chinese scientists and politicians showed great interest in eugenic ideologies, which came to dictate decisions in law-making, family life, and the medical field. Noted American anthropologist Ruth Benedict wrote extensively on Japanese culture and society during and after World War II. Her essentialist portrayals of Japanese people were heavily cited in popular discourse at the time. In 1950s South Africa, interracial marriages and sexual relations were banned by law; antimiscegenation became one of the huge focuses of apartheid resistance activists in later years. We still see the continuation of eugenics-based logic today around the world—in exclusionary immigration laws, cases of incarcerated prison inmates being forcibly sterilized, and the persistence of intelligence testing as a form of measuring people’s “fitness” in a society.
Shortly after World War II and the Nazi Holocaust, the full extent of essentialist, eugenicist thinking became clear. Social constructions of race, and the notion that one can predict psychological or behavioral traits based on external appearance, had become unpopular both within and outside the discipline. It was up to those in the field of physical anthropology at the time to separate physical anthropology from race concepts that supported unscientific and socially damaging agendas. This does not mean that there are no physiological or behavioral differences between different members of the human species. However, going forward, a number of physical anthropologists saw human biological variation as more complicated than simple typologies could describe.
“The New Physical Anthropology”
After 1950, focus steered away from the concept of “race” as a unit of variation and toward understanding why variation exists in populations from an evolutionary perspective. This was outlined by those pioneering the “new physical anthropology,” such as Sherwood Washburn, Theodosius Dobzhansky (Figure 14.10), and Julian Huxley, who borrowed this approach from contemporary population geneticists. Whether using genetic or phenotypic markers as the units of study, “groups” or “clusters” of humans differentiated by these became defined as populations that differ in the frequency of some gene or genes. Anthropologists consider what “makes” a population—a group of individuals potentially capable of or actually interbreeding due to shared geographic proximity, language, ethnicity, culture, and/or values. Put another way, a population is a local interbreeding group with reduced gene flow between themselves and other groups of humans. Members of the same population may be expected to share many genetic traits (and, as a result, many phenotypic traits that may or may not be visible outwardly).
Thinking of humans in terms of populations was part of Julian Huxley’s (1942) “Modern Synthesis”—so named because it helped to reconcile two fundamental principles about evolution that had not been made sense of together before (Figure 14.11). As discussed in Chapter 3, Gregor Mendel (1822‒1884) was able to show that inheritance was mediated by discrete particles (or genes) and not blended in the offspring. However, it was difficult for some 19th-century scientists to accept this model of genetic inheritance at the time because much of biological variation appeared to be continuous and not particulate (take skin color or height as examples). In the 1930s, it was demonstrated that traits could be polygenic and that multiple alleles could be responsible for any one phenotypic trait, thus producing the continuous variation in traits such as eye color that we see today. Thus, Huxley’s “Modern Synthesis” outlines not only how human populations are capable of exchanging genes at the microevolutionary level but also how multiple alleles for one trait (polygenic exchanges) can cause gradual macroevolutionary changes.
Human Variation in Biological Anthropology Today
Many Human Traits Are Nonconcordant
In our studies of human (genetic) variation today, we understand most human traits to be nonconcordant (Figure 14.12). “Nonconcordance” is a term used to describe how biological traits vary independent of each other—that is, they do not get inherited in a correlative manner with other genetically controlled traits. For example, if you knew an individual had genes that coded for tall height, you would not be able to predict if they are lighter-skinned or have red hair. This is different from earlier essentialist views of human variation: the idea that skin color could predict one’s brain function or even “temperament” and tendencies toward criminal behavior.
Human Variation Is Clinal/Continuous (Not Discrete)
Frank B. Livingstone (1928‒2005) wrote: “There are no races, only clines” (1962: 279). A cline is a gradation in the frequency of an allele/trait between populations living in different geographic regions. Human variation cannot be broken into discrete “races,” because most physical traits vary on a continuous or “clinal” basis. One obvious example of this is how human height does not only come in three values (“short,” “medium,” and “tall”) but instead varies across a spectrum of vertical heights achievable by humans all over the world. On the one hand, we can describe human height as exhibiting continuous variation, forming a continuous pattern, but height does not vary according to where people live across the globe and does not exhibit a clinal pattern. On the other hand, skin color variation between populations does show patterning that fits quite well on to how near or far they are from each other on a world map. This makes a trait like skin color clinally distributed worldwide. When large numbers of genetic loci for large numbers of samples were sampled from human populations distributed worldwide during the 1960s and 1970s, the view that certain facets of human diversity were clinally distributed was further supported by genetic data.
To study human traits that are clinally distributed, genetic tests must be performed to uncover the true frequencies of an allele or trait across a certain geographic space. One easily visible example of a clinal distribution seen worldwide is the patterning of human variation in skin color. Whether in southern Asia, sub-Saharan Africa, or Australia, dark brown skin is found. Paler skin tones are found in higher-latitude populations such as those who have lived in areas like Europe, Siberia, and Alaska for millennia. Skin color is easily observable as a phenotypic trait exhibiting continuous variation.
A clinal distribution still derives from genetic inheritance; however, clines often correspond to some gradually changing environmental factor. Clinal patterns arise when selective pressures in one geographic area differ from those in another as well as when people procreate and pass on genes together with their most immediate neighbors. There are several mechanisms, selective and neutral, that can lead to the clinal distribution of an allele or a biological trait. Natural selection is the mechanism that produced a global cline of skin color, whereby darker skin color protects equatorial populations from high amounts of UV radiation; there is a transition of lessening pigmentation in individuals that reside further and further away from the tropics (Jablonski 2004; Jablonski and Chaplin 2000; see Figure 14.13). The ability and inability to digest lactose (milk sugar) among different world communities varies according to differential practices and histories of milk and dairy-product consumption (Gerbault et al. 2011; Ingram et al. 2009). Where malaria seems to be most prevalent as a disease stressor on human populations, a clinal gradient of increasing sickle cell anemia experience toward these regions has been studied extensively by genetic anthropologists (Luzzatto 2012). Sometimes, culturally defined mate selection based on some observable trait can lead to clinal variation between populations as well.
Two neutral microevolutionary processes that may produce a cline in a human allele or trait are gene flow and genetic drift (see Chapter 4). The ways in which neutral processes can produce clinal distributions is seen clearly when looking at clinal maps for different blood groups in the human ABO blood group system (Figure 14.14). For instance, scientists have identified an East-to-West cline in the distribution of the blood type B allele across Eurasia. The frequency of B allele carriers decreases gradually westward when we compare the blood groups of East and Southeast Asian populations with those in Europe. This shows how populations residing nearer to one another are more likely to interbreed and share genetic material (i.e., undergo gene flow). We also see 90%‒100% of native South American individuals, as well as between 70%‒90% of Aboriginal Australian groups, carrying the O allele (Mourant, Kopeć, and Domaniewska-Sobczak 1976). These high frequencies are likely due to random genetic drift and founder effects, in which population sizes were severely reduced by the earliest O allele-carrying individuals migrating into those areas. Over time, the O blood type has remained predominant.
Genetic Variation Is Greater Within Group than Between Groups
One problem with race-based classifications is they relied on an erroneous idea that individuals with particular characteristics would share more similar genes with each other within a particular “race” and share less with individuals of other “races” possessing different traits and genetic makeups. However, since around 50 years ago, scientific studies have shown that the majority of human genetic differences worldwide exist within groups (or “races”) individually rather than between groups. Indeed, most genetic variation we see occurs in Africa, and many variants are shared among individuals on all continents (Figure 14.15).
In 2002, a landmark article by Noah Rosenberg and colleagues explored worldwide human genetic variation using an even-greater genetic data set. They used 377 highly variable markers in the human genome and sampled from 1,056 individuals representative of 52 populations. The markers chosen for study were not ones that code for any expressed genes. Because these regions of the human genome were made of unexpressed genes, we may understand these markers as neutrally derived (as opposed to selectively derived) because they do not code for functional advantages or disadvantages. These neutral genetic markers likely reflect an intricate combination of regional founder effects and population histories. Analyses of these neutral markers allowed scientists to identify that 93%‒95% of global genetic differences, referred to as variance, can be accounted for by within-population differences, while only a small proportion of genetic variance (3%‒5%) can be attributed to differences among major groups (Rosenberg et al. 2002). This research supports the theory that distinct biological races do not exist, even though misguided concepts of race may still have real social and political consequences.
Biological Data Fit Isolation-By-Distance and Out-of-Africa Models
One further note is that the world’s population may be genetically divided into “groups,” “subsets,” “clumps,” or “clusters” that reflect some degree of genetic similarity. These identifiable clusters reflect genetic or geographic distances—either with gene flow facilitated by proximity between populations or impeded by obstacles like oceans or environmentally challenging habitats (Rosenberg et al. 2005). Sometimes, inferred clusters using multiple genetic loci are interpreted by nongeneticists literally as “ancestral populations.” However, it would be wrong to assume from these genetic results that highly differentiated and “pure” ancestral groups ever existed. These groupings reflect differences that have arisen over time due to clinal patterning, genetic drift, and/or restricted or unrestricted gene flow (Weiss and Long 2009). The clusters identified by scientists are arbitrary and the parameters used to split up the global population into groups is subjective and dependent on the particular questions or distinctions being brought into focus (Relethford 2009).
Additionally, research on worldwide genetic variation has shown that human variation decreases with increasing distance from sub-Saharan Africa, where there is evidence for this vast region being the geographical origin of anatomically modern humans (Liu et al. 2006; Prugnolle, Manica, and Balloux 2005; see Figures 14.16 and 14.17). Genetic differentiation decreases in human groups the further you sample data from relative to sub-Saharan Africa because of serial founder effects (Relethford 2004). Over the course of human colonization of the rest of the world outside Africa, populations broke away in expanding waves across continents into western Asia, then Europe and eastern Asia, followed by Oceania and the Americas. As a result, founder events occurred whereby genetic variation was lost, as the colonization of each new geographical region involved a smaller number of individuals moving from the original larger population to establish a new one (Relethford 2004). The most genetic variation is found across populations residing in different parts of sub-Saharan Africa, while other current populations in places like northern Europe and the southern tip of South America exhibit some of the least genetic differentiation relative to all global populations (Campbell and Tishkoff 2008).
Besides fitting nicely into the Out-of-Africa model, worldwide human genetic variation conforms to an isolation-by-distance model, which predicts that genetic similarity between groups will decrease exponentially as the geographic distance between them increases (Kanitz et al. 2018). This is because of the greater and greater restrictions to gene flow presented by geographic distance, as well as cultural and linguistic differences that occur as a result of certain degrees of isolation. Since genetic data conform to isolation-by-distance and Out-of-Africa models, these findings support the abolishment of “race” groupings. This research demonstrates that human variation is continuous and cannot be differentiated into geographically discrete categories. There are no “inherent” or “innate” differences between human groups; instead, variation derives from some degree of natural selection, as well as neutral processes like population bottle-necking (Figure 14.18), random mutations in the DNA, genetic drift, and gene flow through between-mate interbreeding.
Humans Have Higher Homogeneity Compared to Many Other Species
An important fact to bear in mind is that humans are 99.9% identical to one another. This means that the apportionments of human variation discussed above only concern that tiny 0.1% of difference that exists between all humans globally. Compared to other mammalian species, including the other great apes, human variation is remarkably lower. This may be surprising given that the worldwide human population has already exceeded seven billion, and, at least on the surface level, we appear to be quite phenotypically diverse. Molecular approaches to human and primate genetics tells us that external differences are merely superficial. For a proper appreciation of human variation, we have to look at our closest relatives in the primate order and mammalian class. Compared to chimpanzees, bonobos, gorillas and other primates, humans have remarkably low average genome-wide heterogeneity (Osada 2005).
When we look at chimpanzee genetic variation, it is fascinating that western, central, eastern, and Cameroonian chimpanzee groups have substantially more genetic variation between them than large global samples of human DNA (Bowden et al. 2012; Figure 14.19). This is surprising given that all of these chimpanzee groups live relatively near one another in Africa, while measurements of human genetic variation have been conducted using samples from entirely different continents. First, geneticists suppose that this could reflect differential experiences of the founder effect between humans and chimpanzees. As it has been argued that all non-African human populations descended from a small number of anatomically modern humans who left Africa, it would be expected that all groups descended from that smaller ancestral group would be similar genetically. Second, our species is really young, given that we have only existed on the planet for around 150,000 to 300,000 years. This gave humans little time for random genetic mutations to occur as genes get passed down through genetic interbreeding and meiosis. Chimpanzees, however, have inhabited different ecological niches, and less interbreeding has occurred between the four chimpanzee groups over the past six to eight million years compared to the amount of gene flow that occurred between worldwide human populations (Bowden et al. 2012).
Recent advances have now enabled the attainment of genetic samples from the larger family of great apes and the evaluation of genetic variation among bonobos, orangutans, and gorillas alongside that of chimpanzees and humans (Prado-Martinez et al. 2013). Collecting such data and analyzing primate genetic variation has been important not only to elucidate how different ecological, demographic, and climatic factors have shaped our evolution but also to inform upon conservation efforts and medical research. Genes that may code for genetic susceptibilities to tropical diseases that affect multiple primates can be studied through genome-wide methods. Species differences in the genomes associated with speech, behavior, and cognition could tell us more about how human individuals may be affected by genetically derived neurological or speech-related disorders and conditions (Prado-Martinez et al. 2013; Staes et al. 2017). In 2018, a great ape genomic study also reported genetic differences between chimpanzees and humans related to brain cell divisions (Kronenberg et al. 2018). From these results, it may be inferred that cognitive or behavioral variation between humans and the great apes might relate to an increased number of cortical neurons being formed during human brain development (Kronenberg et al. 2018). Comparative studies of human and nonhuman great ape genetic variation highlight the complex interactions of population histories, environmental changes, and natural selection between and within species. When viewed in the context of overall great ape variation, we may reconsider how variable the human species is relatively and how unjustified previous “race” concepts really were.
Phenotypic Traits That Reflect Neutral Evolution
Depending on the trait being observed, different patterns of phenotypic variation may be found within and among groups worldwide. In this subsection, some phenotypic traits that reflect the aforementioned patterns of genetic variation will be discussed.
Looking beyond genetic variation briefly, recent studies have revisited biological anthropology’s earlier themes of externally observable traits, such as skull shape. In the last 20 or so years, anthropologists have evaluated the level to which human cranial shape variation reflects the results from genetic markers, such as those used previously to fit against Out-of-Africa models (Relethford 2004) or those used in the apportionment of human variation between and within groups (Lewontin 1972; Rosenberg et al. 2002). Using larger sample sizes of cranial data collected from thousands of skulls worldwide and a long list of cranial measurements, studies demonstrate a similar decrease in variation with distance from Africa and show that a majority of cranial variation occurs within populations rather than between populations (Betti et al. 2009; Betti et al. 2010; Manica et al. 2007; Relethford 2001; von Cramon-Taubadel and Lycett 2008; see Figure 14.20). The greatest cranial variation is found among skulls of sub-Saharan African origin, while the least variation is found among populations inhabiting places like Tierra del Fuego at the southern tip of Argentina and Chile. While ancient and historical thinkers previously thought “race” categories could reasonably be determined based on skull dimensions, modern-day analyses using more informative sets of cranial traits simply show that migrations out of Africa and the relative distances between populations can explain a majority of worldwide cranial variation (Betti et al. 2009).
This same patterning in phenotypic variation has even been found in studies examining shape variation of the pelvis (Betti et al. 2013; Betti et al. 2014), the teeth (Rathmann et al. 2017), and the human bony labyrinth of the ear (Ponce de León et al. 2018;Figure 14.21). The skeletal morphology of these bones still varies worldwide, but a greater proportion of that variation can still be attributed to the ways in which human populations migrated across the world and exchanged genes with those closer to them rather than those further away. Human skeletal variation in these parts of the body is continuous and nondiscrete. Given the important functions of the cranium and these other skeletal parts, we may infer that the genes that underpin their development have been relatively conserved by neutral evolutionary processes such as genetic drift and gene flow. It is also important to note that while some traits such as height, weight, cranial dimensions, and body composition are determined, in part, by genes, the underlying developmental processes behind these traits are underpinned by complex polygenic mechanisms that have led to the continuous spectrum of variation in such variables among modern-day human populations.
Phenotypic Traits That Reflect Natural Selection
Even though 99.9% of our DNA is the same across all humans worldwide, and many traits reflect neutral processes, there are parts of that remaining 0.1% of the human genome that code for individual and regional differences. Similarly to craniometric analyses that have been conducted in recent decades, human variation in skin color has also been reassessed using new methods and in light of greater knowledge of biological evolution.
New technologies allow scientists to use color photometry to sample and quantify the visible wavelength of skin color, in a way 19th- and 20th-century readers could not. In one report, it was found that 87.9% of global skin color variation can be attributed to genetic differences between groups, 3.2% to those among local populations within regions, and 8.9% within local populations (Relethford 2002). This apportionment differs significantly and is the reverse situation found in the distribution of genetic differences we see when we examine genetic markers such as blood type–related alleles. However, this pattern of human skin color worldwide is not surprising, given that we now understand that past selection has occurred for darker skin near the equator and lighter skin at higher latitudes (Jablonski 2004; Jablonski and Chaplin 2000). While most genetic variation reflects neutral variation due to population migrations, geographic isolation, and restricted gene flow dynamics, some human genetic/phenotypic variation is best explained as local adaptation to environmental conditions (i.e., selection). Given that skin color variation is atypical compared to other genetic markers and biological traits, this, in fact, goes against earlier “race” typologies. This is because recent studies ironically show how so much of genetic variation relates to neutral processes, while skin color does not. It follows that skin color cannot be viewed as useful in making inferences about other human traits.
It is also true that some populations have not been studied extensively in skin pigmentation genetics (e.g., African, Austronesian, Melanesian, Southeast Asian, Indigenous American, and Pacific Islander populations, according to Lasisi and Shriver 2018). Earlier dispersals of these populations, and their local genetic varition, will have contributed to worldwide genetic variation, inclusive of skin pigmentation variation. Gene loci we did not previously appreciate as being linked to pigmentation are now being recognized thanks to better tools, more diverse genetic samples, and more accessible datasets (Quillen et al. 2018). Biological anthropologists look forward to further discoveries elucidating the different selective pressures and population dynamics that influence skin pigmentation evolution.
Social Implications
To finish this chapter, we will consider the social, economic, political, and biological implications of poor understandings of race and the deliberate perpetuation of social and medical racism.
The Black Lives Matter movement (BLM) of 2013 began with the work of racial justice activists and community organizers Alicia Garza, Opal Tometi, and Patrissa Cullors. First incited by the murder of Trayvon Martin, a 17-year-old African American, and the acquittal of the man who shot him, BLM went on to protest against the deaths of numerous Black individuals, most of whom were killed by police officers (for example, Ahmaud Arbery was killed in February of 2020 by two white non-police officers). Some key characteristics of BLM from the start were its decentralized grassroots structure, the role of university students and social media in spreading awareness of the movement, and its embrace of other movements (e.g., climate justice, ending police brutality, feminist campaigns, queer activism, immigration reform, etc.). When George Floyd was murdered by a white police officer on May 25, 2020, the BLM gained new momentum, across 2,000-plus cities in the United States, and among many protesting against historic racism and police brutality in other contexts around the globe. Many in the biological anthropology community have responded to these events with a great dedication to working against systemic racism in society and institutions (American Association of Biological Anthropologists 2020).
BLM continues to be an important movement, as is evidenced in the degree of community organizing, mutual aid efforts, calls for political reform, progress toward curriculum reform and equality, inclusion and diversity (EDI) work in businesses and universities, the removal of monuments honoring historical figures associated with slavery and racism, and many other important actions. Garza (2016) writes: “The reality is that race in the United States operates on a spectrum from black to white … the closer you are to white on that spectrum, the better off you are.” Tometi (2016) has stated: “We need [a human rights movement that challenges systemic racism] because the global reality is that Black people are subject to all sorts of disparities in most of our challenging issues of our day. I think about climate change, and how six of the ten worst impacted nations by climate change are actually on the continent of Africa.” In the words of Cullors (2016), “Black Lives Matter is our call to action. It is a tool to reimagine a world where Black people are free to exist, free to live. It is a tool for our allies to show up differently for us.” We gather from their words the importance of learning from the egregious role that anthropologists have played in the past, recognizing the legacies of “scientific” justifications for eugenics and racism in our society today, and proactively working toward environmental and social equity.
Another major industry that engages in the quantification and interpretation of human variation is medical and clinical work (National Research Council [U.S.] Committee on Human Genome Diversity 1997). Large-scale genomic studies sampling from human populations distributed worldwide have produced detailed knowledge on variation in disease resistance or susceptibility between and within populations. Let’s think about drug companies who develop medicines for Black patients particularly. The predispositions to particular diseases are higher among people of African descent than some pharmaceutical businesses have taken into account. Through targeted sampling of various world groups, clinical geneticists may also identify genetic risk factors of certain common disorders such as chronic heart disease, asthma, diabetes, autoimmune diseases, and behavioral disorders. Having an understanding of population-specific biology is crucial in the development of therapies, medicines, and vaccinations, as not all treatments may be suitable for every human, depending on their genotype. During diagnosis and treatment, it is important to have an evolutionary perspective on gene-environment relationships in patients. Typological concepts of “race” are not useful, given that most racial groups (whether self-identified or not) popularly recognized lack homogeneity and are, in fact, variable. Cystic fibrosis, for instance, occurs in all world populations but can often be underdiagnosed in populations with African ancestry because it is thought of as a “white” disease (Yudell et al. 2016).
Sociologists, law scholars, and professors of race studies have written extensively on how genetic/technological/medical revolutions impact people of color. In her book, Fatal Invention: How Science, Politics, and Big Business Re-create Race in the Twenty-First Century (2013), Professor Dorothy E. Roberts writes about how technological advances have been used in resuscitating race as a biological category for dividing humans in essentialist ways (Figure 14.23). She notes how members of law enforcement have engaged in racial profiling, sometimes with the use of machine-learning and facial-recognition technologies. Ancestry-testing services also purport to tell us “what” we are and to insist that this information is “written” in our genes. Such advertising campaigns obscure the nuances of genetic variation with the primary motive of tapping into people’s desire to “know themselves” and driving up profits for their businesses. Commercial genetic testing reinforces the idea that genes map neatly onto race, all while generating massive stores of data in DNA databases. In Roberts’s view, the myth of the biological concept of race being perpetuated in these ways undermines a just society and reproduces racial inequalities.
The COVID-19 pandemic has had a significant impact on the world’s population, particularly people living in the economic Global South and many Black, Indigenous and communities of color residing in the Global North. We have witnessed disproportionately high numbers of COVID-related deaths and infection cases among marginalized groups. Many immigrants and ethnic minorities in various societies have also experienced scapegoating and blame directed at them for being the source of COVID-19 spread.
To inform us on how to interpret this current worldwide pandemic, historians and anthropologists are looking back at the lessons learned from past instances of racist medicine (discriminatory practices based on broader social discrimination) and medical racism (application of discriminatory practices justified on medical grounds). Historically, who could become doctors and medical professionals was often racialized, gendered, and class specific. This made it difficult for many to overcome prejudices against women, Black people, Indigenous individuals, or other people of color from becoming doctors and clinical researchers in places such as South Africa and the United States. This, in turn, affects the sorts of information we know about health levels and health outcomes among these very groups. In the past decade, long-overdue attention is finally being paid to how race affects biological outcomes. For instance, researchers have focused on the negative legacies of racial discrimination and racism-induced stress on hormone (im)balances, mental health disorders, cardiovascular disease prevalence, and other health outcomes (Kuzawa and Sweet 2009; Shonkoff, Slopen, and WIlliams 2021; Williams 2018). The technology and standards of protocol in medical testing have been scrutinized (for more on how pulse oximeters were not designed with nonwhite patients in mind, for example, see Sjoding et al. 2020). Scholars of race and medicine have also written on how illness and disease spread have often been used to perpetuate societal prejudices. This manifests as xenophobic tendencies at a societal level, such as the blaming of “outgroups” and increased “in-group” protectiveness. Overreliance on the idea that people are “inherently” disease carriers due to genetic or biological reasons leads to improper accounting for socioeconomic or infrastructural issues that lead to differential disease prevalence amongst minority communities. (For more on race and COVID, see Tsai 2021 as well as this textbook’s Chapter 16: Contemporary Topics: Human Biology and Health.)
It is important to remember that while it is possible to look for clues about one’s ancestry or geographic origin based on skull morphology, again, the amount of distinctiveness in any given sample makes it impossible to distinguish whether a cranium belongs to one group (Relethford 2009). Individuals can vary in their skeletal dimensions by continental origin, country origin, regional origin, sex, age, environmental factors, and the time period in which they lived, making it difficult to assign individuals to particular categories in a completely meaningful way (Ousley, Jantz, and Freid 2009). When forensic reports and scientific journal articles give an estimation of ancestry, it is crucial to keep in mind that responsible assignments of ancestry will be done through robust statistical testing and stated as a probability estimate. Today, we also live in a more globalized world where a skeletal individual may have been born originally to parents of two separate traditional racial categories. In contexts of great heterogeneity within populations, this definitely adds difficulty to the work of forensic scientists and anthropologists preparing results for the courtroom (genetic testing may be comparatively more helpful in such situations).
Dig Deeper: Measuring FST
Richard Lewontin (1929‒) is a biologist and evolutionary geneticist who authored an article evaluating where the total genetic variation in humans lies. Titled “The Apportionment of Human Diversity” (Lewontin 1972), the article addressed the following question: On average, how genetically similar are two randomly chosen people from the same group when compared to two randomly chosen people from different groups?
Lewontin studied this problem by using genetic data. He obtained data for a large number of different human populations worldwide using 17 genetic markers (including alleles that code for various important enzymes and proteins, such as blood-group proteins). The statistical analysis he ran used a measure of human genetic differences in and among populations known as the fixation index (FST).
Technically, FST can be defined as the proportion of total genetic variance within a subpopulation relative to the total genetic variance from an entire population. Therefore, FST values range from 0 to 1 (or, sometimes you will see this stated as a percentage between 0% and 100%). The closer the FST value of a population (e.g., the world’s population) approaches 1, the higher the degree of genetic differentiation among subpopulations relative to the overall population (see Figure 14.24 for a detailed illustration).
In his article, Lewontin (1972) identified that most of human genetic differences (85.4%) were found within local subpopulations (e.g., the Germans or Easter Islanders), whereas 8.3% were found between populations within continental human groups, and 6.3% were attributable to traditional “race” groups (e.g., “Caucasian” or “Amerind”). These findings have been important for scientifically rejecting the existence of biological races (Long and Kittles 2003).
Talking About Human Biological Variation Going Forward
To conclude, utilizing the term races to describe human biological variation is not accurate or productive. Using a select few hundred genetic loci, or perhaps a number of phenotypic traits, it may be possible to assign individuals to a geographic ancestry, but what constitutes a bounded genetic or geographical grouping is both arbitrary and potentially harmful owing to ethical and historical reasons. The discipline of biological anthropology has moved past typological frameworks that shoehorn continuously variable human populations into discrete and socially constructed subsets. Improvements in the number of markers, the genetic technologies used to study variation, and the number of worldwide populations sampled have led to more nuanced understandings of human variation. It is of utmost importance that scientists make the following points clear to the public:
- Today, we refer to different local human groups as “populations.” What constitutes a population should be carefully defined in scientific reports based on some geographical, linguistic, or cultural criteria and some degree of relativity to other closely or distantly related human groups.
- Humans have significantly less genetic variation than other primates and mammals, and all human beings on Earth share 99.9% of their overall DNA. Some of the remaining 0.1% of human variation varies on a clinal or continuous basis, such as can be seen when looking at ABO blood-type polymorphisms worldwide.
- Many biological characteristics in humans are actually determined nonconcordantly and/or polygenically. Therefore, superiority or inferiority in human behavior or body form cannot justifiably be linked to fixed and innate differences between groups.
- Genetic distances are correlated with geographic distances among the global human population. This is especially apparent when we consider that genetic variation is highest in sub-Saharan Africa, and average genetic heterogeneity decreases in populations further away from the African continent in accordance with the migratory history of anatomically modern Homo sapiens.
- The effects of gene flow, genetic drift, and population bottlenecking are reflected in some phenotypic traits, such as cranial shape.
- We recognize other traits, like skin color and lactase persistence, to be the products of many millennia of natural selective pressures influencing human biology from the external environment.
Taken together, genetic analyses of human variation do not support 20th-century (or even-earlier) concepts of race. In discussions about human variation, these genomic results help clarify how biological variation is distributed across the human population today. Taking care to think about and debate the nature of human variation is important, because although the effects and events that produced genetic differences among groups occurred in the ancient past, sociocultural concepts about race and ethnicity continue to have real social, economic, and political consequences.
Beyond talking about variation in the university setting, it is important that teachers, researchers, and students of anthropology recognize and assume the responsibility of influencing public perspectives of human variation. Race-based classification systems were developed during the colonial era, the transatlantic trafficking of kidnapped Africans and the so-called “Scientific Revolution” by the first “anthropologists” and scholars of humankind’s variation. Unfortunately, some of their early ideas have persisted and evolved into present-day lived realities. Some of today’s politicians and socioeconomic bodies have racially charged agendas that promote racism or certain kinds of economic or racial inequalities. As anthropologists, we must acknowledge that while human “races” are not a biological reality, their status as a (misguided) social construction does have real consequences for many people (Antrosio 2011).
In other words, while “race” is a sociocultural invention, the treatment different individuals receive due to their perceived “race” can have significant financial, emotional, sociopolitical, and physiological costs. However—and importantly assuming a “color-blind” position when it comes to the topics of “race” and ethnicity (especially in political discussions) is actually counterproductive, because the negative social consequences of modern “race” ideas could be ignored, making it harder to examine and address instances of discrimination properly (Wise 2010). Rather than shy away from these topics, we can use our scientific findings to establish socially relevant and biologically accurate ideas concerning human diversity. Today, research into genetic and phenotypic differentiation among and within various human populations continues to expand in its scope, its technological capabilities, its sample sizes, and its ethical concerns. It is thanks to such scientific work done in the past few decades that we now have a deeper understanding not only of how humans vary but also of how we are biologically a rather homogenous, intermixing world population.
Summary
Historically, most concepts of race were shaped by religious and early ‘scientific’ attempts to classify people, many of which justified inequality and racism. Today, biological anthropology emphasizes that human variation is continuous (clinal), polygenic, and shaped by both evolutionary pressures and neutral processes. Misunderstandings of race, however, continue to have serious social and medical consequences; evident in systemic racism and inequities in health care.
Biological anthropologists now play a critical role in discrediting myths about race. By studying human variation, we can begin to understand evolutionary processes, adaptation, and the social implications of differences among human populations. Modern research shows that that humans are far more genetically homogenous than many other species, reinforcing a conclusion that ‘race’ is not a biological reality but a powerful social construct with real effects. Through evolutionary history and genetics, human diversity can be researched and understood, rather than than through racial categories.
Review Questions
- How is the genetic variation of the human species distributed worldwide?
- What evolutionary processes are responsible for producing genotypic/phenotypic variation within and between human populations?
- Should we continue to attribute any value to “race” concepts older than 1950, based on our current understandings of human biological variation?
- How should we communicate scientific findings about human biological variation more accurately and responsibly to those outside the anthropological discipline?
Key Terms
Age of Discovery: A period between the late 1400s and late 1700s when European explorers and ships sailed extensively across the globe in pursuit of new trading routes and territorial conquest.
Ancestry: Biogeographical information about an individual, traced either through the study of an individual’s genome, skeletal characteristics, or some other form of forensic/archaeological evidence. Anthropologists carry out probabilistic estimates of ancestry. They attribute sets of human remains to distinctive “ancestral” groups using careful statistical testing and should report ancestry estimations with statistical probability values.
Binomial nomenclature: A system of naming living things developed by Linnaeus in the 1700s. It employs a scientific name made up of two italicized Latin or Greek words, with the first word capitalized and representative of an organism’s genus and the second word indicating an organism’s species (e.g., Homo sapiens, Australopithecus afarensis, Pongo tapanuliensis, etc.).
Biological anthropology: A branch of study under anthropology (the study of humankind) that focuses on when and where humans and our human ancestors first originated, how we have evolved and adapted globally over time, and the reasons why we see biological variation among humans worldwide today.
Biological determinism: The erroneous concept that an individual’s behavioral characteristics are innate and determined by genes, brain size, or other physiological attributes—and, notably, without the influence of social learning or the environment around the individual during development.
Bony labyrinth: A system of interconnected canals within the auditory (ear- or hearing-related) apparatus, located in the inner ear and responsible for balance and the reception of sound waves.
Cline: A gradient of physiological or morphological change in a single character or allele frequency among a group of species across environmental or geographical lines (e.g., skin color varies clinally, as, over many generations, human groups living nearer the equator have adapted to have more skin pigmentation).
Continuous variation: This term refers to variation that exists between individuals and cannot be measured using distinct categories. Instead, differences between individuals within a population in relation to one particular trait are measurable along a smooth, continuous gradient.
Cystic fibrosis: A genetic disorder in which one defective gene causes overproduction and buildup of mucus in the lungs and other bodily organs. It is most common in northern Europeans (but also occurs in other world populations).
Ecological niche: The position or status of an organism within its community and/or ecosystem, resulting from the organism’s structural and functional adaptations (e.g., bipedalism, omnivorous diets, lactose digestion, etc.).
Essentialism: A belief or view that an entity, organism, or human grouping has a specific set of characteristics that are fundamentally necessary to its being and classification into definitive categories.
Ethnicity: A term used commonly in an interchangeable way with the term race, complicated because how different people define this term depends on the qualities and characteristics they use to assign a label or identity to themselves and/or others (which may include aspects of family background, skin color, language(s) spoken, religion, physical proportions, behavior and temperament, etc.).
Eugenics: A set of beliefs and practices that involves the controlled selective breeding of human populations with the hope of improving their heritable qualities, especially through surgical procedures like sterilization and legal rulings that affect marriage rights for interracial couples.
Gene flow: A neutral (or nonselective) evolutionary process that occurs when genes get shared between populations.
Genetic drift: A neutral evolutionary process in which allele frequencies change from generation to generation due to random chance.
Heterogeneity: The quality of being diverse genetically.
Homogenous: The quality of being uniform genetically.
Human diversity: Human diversity is a measure of variation that may describe how many different forms of human there are, separated or clustered into groups according to some genetic, phenotypic, or cultural trait(s). The term can be applied to culture (in which case humans can be described as significantly diverse) or genetics (in which case humans are not diverse because all humans on Earth share a majority of their genes).
Human variation: Differences in biology, physiology, body chemistry, behavior, and culture. By measuring these differences, we understand the degrees of variation between individuals, groups, populations, or species.
Isolation-by-distance model: A model that predicts a positive relationship between genetic distances and geographical distances between pairs of populations.
Monogenetic: Pertaining to the idea that the origin of a species is situated in one geographic region or time (as opposed to polygenetic).
Mutation: A gene alteration in the DNA sequence of an organism. As a random, neutral evolutionary process that occurs over the course of meiosis and early cell development, gene mutations are possible sources of variation in any given human gene pool. Genetic mutations that occur in more than 1% of a population are termed polymorphisms.
Natural selection: An evolutionary process whereby certain traits are perpetuated through successive generations, likely owing to the advantages they give organisms in terms of chances of survival and/or reproduction.
Nonconcordance: The fact of genes or traits not varying with one another and instead being inherited independently.
Otherness: In postcolonial anthropology, we now understand “othering” to mean any action by someone or some group that establishes a division between “us” and “them” in relation to other individuals or populations. This could be based on linguistic or cultural differences, and it has largely been based on external characteristics throughout history.
Out-of-Africa model: A model that suggests that all humans originate from one single group of Homo sapiens in (sub-Saharan) Africa who lived between 100,000 and 315,000 years ago and who subsequently diverged and migrated to other regions across the globe.
Physical anthropology: This used to be the more common name given to the subdiscipline of anthropology centered upon the study of human origins, evolution and variation (also see biological anthropology above). This name for the field has gradually become less popular due to two reasons: first, it may not reflect our interests in other aspects of humankind that are not physical (such as those behavioral, cultural and spiritual), and second, using this term popular in the early decades of our field may be viewed by some as harkening back to a time when biological anthropologists conducted their work in unethical ways.
Polygenetic: Having many different ancestries, as in older theories about human origins that involved multiple traditional groupings of humans evolving concurrently in different parts of the world before they merged into one species through interbreeding and/or intergroup warfare. These earlier suggestions have now been overwhelmed by insurmountable evidence for a single origin of the human species in Africa (see the “Out-of-Africa model”).
Polymorphism: A genetic variant within a population (caused either by a single gene or multiple genes) that occurs at a rate of over 1% among the population. Polymorphisms are responsible for variation in phenotypic traits such as blood type and skin color.
Population: A group of humans living in a particular geographical area, with more local interbreeding within-group than interbreeding with other groups. A limited or restricted amount of gene flow between populations can occur due to geographical, cultural, linguistic, or environmental factors.
Population bottlenecking: An event in which genetic variation is significantly reduced owing to a sharp reduction in population size. This can occur when environmental disaster strikes or as a result of human activities (e.g., genocides or group migrations). An important example of this loss in genetic variation occurred over the first human migrations out of Africa and into other continental regions.
Prejudice: An unjustified attitude toward an individual or group that is not based on reason, whether positive (and showing preference for one group of people over another) or negative (and resulting in harm or injury to others).
Race: The identification of a group based on a perceived distinctiveness that makes that group more similar to each other than they are to others outside the group. This may be based on cultural differences, genetic parentage, physical characteristics, behavioral attributes, or something arbitrarily and socially constructed. As a social or demographic category, perceptions of “race” can have real and serious consequences for different groups of people. This is despite the fact that biological anthropologists and geneticists have demonstrated that all humans are genetically homogenous and that more differences can be found within populations than between them in the overall apportionment of human biological variation. This term is sometimes used interchangeably with ethnicity.
Racism: Any action or belief that discriminates against someone based on perceived differences in race or ethnicity.
Scientific Revolution: A period between the 1400s and 1600s when substantial shifts occurred in the social, technological, and philosophical sense, when a scientific method based on the collection of empirical evidence through experimentation was emphasized and inductive reasoning was used to test hypotheses and interpret their results.
Typological: Of or describing an assortment system that relies on the interpretation of qualitative similarities or differences in the study of variation among objects or people. The categorization of cultures or human groups according to “race” was performed with a typological approach in the earliest practice of anthropology, but this practice has since been discredited and abandoned.
Variance: In statistics, variance measures the dispersal of a set of data around the mean or average value.
For Further Exploration
Videos
American Medical Association (AMA). 2020. “Examining Race-Based Medicine.” YouTube, October 29. Accessed June 4, 2023.
Crenshaw, Kimberlé. 2016. “The Urgency of Intersectionality.” YouTube, December 7. Accessed June 4, 2023.
Golash-Boza, Tanya. 2018. “What Is Race? What Is Ethnicity? Is There a Difference?.” YouTube, October 28. Accessed June 4, 2023.
Lasisi, Tina. 2020. “How Hair Reveals the Futility of Race Categories.” National Museum of Natural History webinar, October 21.
Lasisi, Tina. 2022. “Where Does My Skin Color Come From?.” PBS Terra, August 18. Accessed June 4, 2023.
PBS Origins. 2018. “The Origin of Race in the USA.” YouTube, April 3. Accessed June 4, 2023.
Roberts, Dorothy. 2016. “The Problem with Race-Based Medicine.” YouTube, March 4. Accessed June 4, 2023.
Vox. 2015. “The Myth of Race, Debunked in 3 Minutes.” YouTube, January 13. Accessed June 4, 2023.
Podcast Episodes
Kwong, Emily, and Rebecca Ramirez. 2021. “Here’s a Better Way to Talk about Hair: A 16 Minute Listen with Tina, Lasisi” NPR Short Wave, October 6. Accessed June 4, 2023.
Speaking of Race. 2020. “Race and Health series.” Speaking of Race, April 10. Accessed June 4, 2023.
Websites
Choices Program. 2023. “An Interactive Timeline: Black Activism and the Long Fight for Racial Justice.” Choices Program, Brown University [Interactive Timeline], Updated February, 2023.
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Leslie E. Fitzpatrick, Ph.D., Independent Archaeological Consultants
This chapter is a revision from "Chapter 14: Human Variation: An Adaptive Significance Approach” by Leslie E. Fitzpatrick. In Explorations: An Open Invitation to Biological Anthropology, first edition, edited by Beth Shook, Katie Nelson, Kelsie Aguilera, and Lara Braff, which is licensed under CC BY-NC 4.0.
Learning Objectives
- Distinguish between adaptations and adjustments as ways of coping with environmental stressors.
- Provide examples of adjustments humans use to cope with thermal stressors.
- Describe how specific patterns of human adaptations and adjustments are correlated to natural selection processes.
- Summarize the role of solar radiation in variations of human skin tone, and explain why reduced pigmentation is advantageous in northern latitudes.
- Compare and contrast the various genetic mutations present in Tibetan and Ethiopian populations that allow them to survive at high altitudes.
- Define the relationship between specific genetic mutations in some human populations and certain infectious diseases, such as the sickle-cell trait mutation and malarial infection.
As early humans left Africa and spread across the globe, they faced numerous challenges related to their new environments. Beyond genetically influenced changes in physiology as a result of evolution, humans have developed lifestyle strategies to cope with and even thrive in a wide range of habitats. The ways populations of humans met such challenges, coupled with their geographic separation throughout the majority of the last two hundred thousand years, have led to the many forms of adaptation in our species. This chapter focuses on the complexities of modern human variation through the lens of human evolutionary history.
Stress and Homeostasis
All organisms, including humans, must maintain a baseline of normal functions within their cells, tissues, and organs to survive. This constancy of internal functions is referred to as homeostasis. Homeostatic regulation, however, may be disrupted by a variety of both external and internal stimuli known as stressors. Within limits, all organisms have evolved certain physiological mechanisms to respond to stressors in an effort to maintain homeostasis. The range of changes in the physiology (function), morphology (form), and/or behavior of organisms in response to their environments and potential stressors is regulated by its phenotypic plasticity. Coping with these stressors led to the development of both adjustments (behavioral, acclimatory, and developmental) and adaptations, which are explained in detail in the following sections.
Adjustments and Adaptations
Adjustments
The term adjustment refers to an organism’s nongenetic way of coping with the stressors of its environment. Although adjustments themselves are nongenetic in nature, the ability of an organism to experience or develop an adjustment is based on its phenotypic plasticity, which is linked to its evolutionarily guided genetic potential. Adjustments occur exclusively on the individual level. As such, different individuals within a population may experience a wide range of possible adjustments in response to a similar stressor. In general, the three main forms of adjustment are: behavioral, acclimatory, and developmental.
Behavioral Adjustments
When you are cold, do you reach for a blanket? When you are warm, do you seek out shelter cooled by an air-conditioning system? If so, you have likely been influenced to do so by the culture in which you were raised. As noted earlier in this textbook, the term culture refers to a collection of shared, learned beliefs and behaviors among individuals within a discrete population. Behavioral adjustments are regarded as cultural responses to environmental stressors. These adjustments are temporary in nature and, since they are nongenetic, must be constantly altered to meet novel situations posed by the environment. For example, divers are able to reach extraordinary depths (in excess of 300 meters below the surface) within the water through the use of a specialized mixture of gasses for breathing, an apparatus for the delivery of the gasses, protective clothing, and gear to increase visibility. The deeper a diver descends, the more atmospheric pressure the diver experiences, resulting in increased levels of potentially toxic byproducts of respiration within the body. In addition, with increased depth there is a decrease in the ambient temperature of the water and a decrease in the availability of light within the visible spectrum. Deep-water divers are well-versed in the environmental stressors of open waters and employ a variety of strategies based on behavioral adjustments to meet such demands. From wearing protective clothing to help maintain the body’s core temperature to waiting at a specific depth for a prescribed period of time to facilitate the expulsion of nitrogen gas that may have accumulated within the bloodstream, divers employ numerous behavioral adjustments to ensure their safety (Figure 15.1). Without these culturally mediated behavioral adjustments, a deep-water diver’s first dive would also be their last.
In many developing countries, the use of refrigeration for the storage of perishable food products is uncommon; therefore, individuals within these cultures have developed a variety of behavioral adjustment strategies related to food preparation to address possible food spoilage. Through a cross-cultural analysis of spice use in recipes, Paul Sherman and Jennifer Billing (1999) determined that cultures closest to the equator, where temperatures are hotter, tend to use both a greater number and a wider variety of plant-based spices with bacteria-inhibiting phytochemical properties (e.g., garlic and onion). Antimicrobial properties of spices permits the consumption of foods, particularly animal-based protein sources, for a period of time beyond that which would be considered safe. There are some acclimatory adjustment benefits to the use of some pungent spices as well, which are explored in the following section.
Acclimatory Adjustments: Thermal Stressors
Acclimatory adjustments are temporary, reversible changes in an organism’s physiology in response to environmental stressors. Although they are not genetically determined, the range of acclimatory adjustments that an organism is capable of producing is linked to its underlying phenotypic plasticity and the duration and severity of the stressor. A good example of this is the human response to varying ambient temperatures.
To understand human adjustments, we must first understand the thermodynamic mechanisms through which heat may be gained or lost. The four pathways for this are conduction, convection, evaporation, and radiation (Figure 15.2).
Through conduction processes, heat will move from a warmer body to a cooler one through direct contact. An example of this is when you accidentally touch a hot cooktop with your hand and the heat is transferred from the cooktop to your skin.
With convection, when a warm body is surrounded by a cooler fluid (e.g., air or water), heat will be transferred from the warmer body to the cooler fluid. This is why we will often employ the behavioral adjustment of wearing multiple layers of clothing during the winter in an effort to prevent heat loss to the cooler atmosphere. Conversely, if your body temperature is cooler than that of the air surrounding you, your body will absorb heat.
Depending on your physical condition, most people will begin to sweat around 37.2℃ to 37.7℃ (98.9℉–99.9℉). Sweating is an example of evaporation, which occurs when a liquid, such as the water within our bodies, is converted to a gas. Phase conversions, such as those underlying the evaporative processes of transforming liquids to gasses, require energy. In evaporation, this energy is in the form of heat, and the effect is to cool the body.
The final mechanism for heat loss within the human body is radiation, through which energy in the form of electromagnetic waves is produced at a wavelength that typically lies below that which is visible to the human eye. Although humans gain and lose heat from their bodies through radiation, this form of heat transfer is not visible. Humans are capable of losing and gaining heat through conduction, convection, and radiation; however, heat may not be gained through evaporation.
As the ambient temperature decreases, it becomes increasingly difficult for the human body to regulate its core temperature, which is central to the maintenance of homeostasis. When an individual’s body temperature falls below 34.4℃ (93.9°F), the brain’s hypothalamus becomes impaired, leading to issues with body temperature control. A total loss of the ability to regulate body temperature occurs around 29.4℃ (84.9°F), which may result in death. When the ambient temperature falls below the critical temperature of 31℃ (87.8°F), a nude human body that is at rest will respond with a series of physiological changes to preserve homeostasis (Figure 15.3).
The human body experiences two main types of physiological responses to colder temperatures: those that increase the production of heat and those that seek to retain heat. The production of heat within the body is accomplished through short-term increases in the body’s basal metabolic rate, such as shivering to increase muscular metabolism. An organism’s basic metabolic rate is a measure of the energy required to maintain necessary body processes when the organism is at rest. Increases in basal metabolic rates, such as when we shiver from the cold, require increased consumption of energy-providing nutrients. Of course, such increases in metabolic rates are not infinite, as we may only consume a finite amount of nutrients. As with all acclimatory adjustments, an increase in the basal metabolic rate is merely temporary.
Of the physiological mechanisms to preserve heat already in the body, the most notable is vasoconstriction, or the constriction of peripheral capillaries in the skin. The decreased surface area of the capillaries through vasoconstriction results in less heat reaching the surface of the skin where it would be dissipated into the atmosphere. Vasoconstriction also leads to the maintenance of heat near the core of the body where the vital organs are located. As a trade-off, though, individuals are more at risk of cold-related injuries, such as frost-bite, which can lead to tissue necrosis (tissue death) in regions of the body that are most distant from the core (e.g., fingers, toes, nose, ears, cheeks, chin, etc.).
Just as cold stress presents challenges to maintaining homeostasis, heat does as well. In hot climates, the body will absorb heat from its surroundings (through conduction, convection, and radiation), resulting in potential heat-related disorders, such as heat exhaustion. When the human body is exposed to ambient temperatures above 35℃ (95°F), excess body heat will be lost primarily through evaporative processes, specifically through sweating. All humans, regardless of their environment, have approximately the same number of sweat glands within their bodies. Over time, individuals living in hot, arid environments will develop more sensitive forms of sweat glands resulting in the production of greater quantities of sweat (Best, Lieberman, and Kamilar 2019; Pontzer et al. 2021). In an effort to prevent dehydration due to this form of acclimatory adjustment, there will be an additional reduction in the volume of urine produced by the individual (Pontzer et al. 2021).
As noted in the previous section, some cultural groups, particularly those in equatorial regions, add pungent spices to their foods to inhibit the colonization of bacteria (Sherman and Billing 1999). Although adding spices to decrease spoilage rates is a behavioral adjustment, the application of some forms of peppers triggers an acclimatory adjustment as well. Compounds referred to as capsaicinoids are the secondary byproducts of chili pepper plants’ metabolism and are produced to deter their consumption by some forms of fungi and mammals. When mammals, such as humans, consume the capsaicinoids from chili peppers, a burning sensation may occur within their mouths and along their digestive tracts. This burning sensation is the result of the activation of capsaicin receptors along the body’s nerve pathways. Although the peppers themselves may be at ambient temperature so their consumption is not causing any form of body temperature increase, the human body perceives the pepper as elevating its core temperature due to the activation of the capsaicin receptors. This causes the hypothalamus to react, initiating sweating in an attempt to lower body temperature and maintain homeostasis. The increased piquancy (application of pungent spices to food) as a means of inhibiting food-borne bacterial colonization in warm climates, as well as spices’ ability to trigger sweating processes as a method for cooling the body, is an example of the intersection between behavioral and acclimatory adjustments that utilized within certain populations.
In addition to increased sweat production to maintain homeostasis in excess heat, vasodilation may occur (Figure 15.4). Vasodilation is an expansion of the capillaries within the skin leading to a more effective transfer of heat from within the body to the exterior to allow conductive, convective, radiative, and evaporative (sweating) processes to occur.
Physiologically based acclimatory adjustments to hot, dry climates may be complemented by behavioral adjustments as well. For example, individuals in such climates may limit their physical activity during the times of day when the temperature is typically the hottest. Additionally, these individuals may wear loose-fitting clothing that covers much of their skin. The looseness of the clothing allows for air to flow between the clothing and the skin to permit the effective evaporation of sweat. Although it may seem counterintuitive to cover one’s body completely in a hot climate, the covering of the skin keeps the sun’s rays from directly penetrating the skin and elevating the body’s core temperature.
Acclimatory Adjustments: Altitudinal Stressors
The challenges posed by thermal conditions are but one form of environmental stressor humans must face. High-altitude environments, which are defined as altitudes in excess of 2,400 meters above sea level (masl) or 7,874 feet above sea level (fasl), pose additional challenges to the maintenance of homeostasis in humans. Some of the main stressors encountered by those living within high-altitude environments include decreased oxygen availability, cold temperatures, low humidity, high wind speed, a reduced nutritional base, and increased solar radiation levels. Of these challenges, the most significant is the decreased availability of oxygen.
To visualize how altitude affects the availability of oxygen, imagine two balloons that are each filled with the same quantity of oxygen molecules. One of these balloons is positioned at sea-level and the other is placed high upon a mountain peak. For the balloon at sea level, there is more atmospheric pressure pressing down on the molecules within this balloon. This leads to the oxygen molecules within the sea level balloon being forced into a more compact organization. In contrast, the mountain peak balloon has less atmospheric pressure pressing down on it. This leads to the oxygen molecules within that balloon spreading out from each other since they are not being forced together quite as strongly. This example highlights the availability of oxygen molecules in each breath than we take in low- versus high-altitude environments. At 5,500 masl (approximately 18,000 fasl), the atmospheric pressure is approximately 50% of its value at sea level (Peacock 1998). At the peak of Mount Everest (8,900 masl or approximately 29,200 fasl), the atmospheric pressure is equivalent to only about 30% of their sea level amounts (Peacock 1998; Figure 15.5).
Due to decreased availability of oxygen at higher altitudes, certain acclimatory adjustments are required to ensure the maintenance of homeostasis for individuals other than those who were gestated, born, and raised at high altitude. For these people, their rate of breathing will increase to permit greater quantities of air containing oxygen into the lungs when they ascend into higher altitude environments. An increased speed and depth of breathing, which is referred to as hyperpnea, is not sustainable indefinitely; thus, the rate of breathing begins to decrease as the person becomes acclimatized to the altitude. During the initial phases of high-altitude-related hyperpnea, the heart begins to beat faster but the amount of blood pushed through during each beat decreases slightly. In addition, the body will divert energy from noncritical bodily functions, such as digestive processes.
Once the atmospheric oxygen reaches the alveoli (small air sacs) in the lungs, it spreads across the alveolar membrane and enters erythrocytes (red blood cells). As oxygen reaches the alevoli’s erythrocytes, it loosely binds with hemoglobin (an iron-rich protein) contained in the erythrocytes. When the erythrocytes carrying the hemoglobin-bound oxygen molecules reach capillaries where the partial pressure of oxygen is relatively low, oxygen will be released by the hemoglobin so that it is free for diffusion into body cells. Similar to acclimatory adjustments related to thermal conditions (e.g., shivering or sweating), those related to high altitude may not be infinitely sustained due to their energetically expensive nature.
Although the long-term acclimatory adjustments that an individual from low altitude experiences in a high-altitude environment may permit them to reside there successfully, reproduction within such settings is frequently complicated. With increased altitude comes an increased risk of miscarriage, lower birth weights, and higher infant mortality rates. As the pregnant person’s body seeks to preserve its own homeostasis, there is often a decreased rate and volume of blood flow to the uterus as compared to a pregnant person of similar physiological condition at a lower altitude (Moore, Niermeyer, and Zamudio 1998). This results in a decrease in the amount of oxygen that will be passed through the uterus and placenta to the developing fetus. In addition, pregnant people who experience pregnancy at higher altitudes are more prone to developing preeclampsia (severe elevation of blood pressure), which is linked to increased rates of both fetal and maternal death (Moore, Niermeyer, and Zamudio 1998; Figure 15.6).
Developmental Adjustments
Developmental adjustments occur only in individuals who spent their developmental period (i.e., childhood and adolescence) within a high-altitude environment; they do not apply to those who moved into these environments in the post developmental (i.e., adult) phase. Furthermore, the degree of developmental adjustment within an individual is directly related to their underlying phenotypic plasticity as well as the amount of time during the crucial growth and development period that the individual resides within the challenging environment. Although humans have the remarkable capacity to develop and survive within environments that are not overly conducive to the successful maintenance of homeostasis, there are definitely physiological costs associated with this ability.
In general, high-altitude natives tend to grow more slowly and physically mature later than their low-altitude counterparts (Figure 15.7). Lowered growth and maturity rates are linked not only to the increased physiological demands placed on the body due to the decreased partial pressure of oxygen but also to reductions in the quality of the nutritional base at higher altitudes. Increased terrain complexity, elevated solar radiation levels, and higher wind speeds coupled with the lower temperatures and humidity levels found at high altitudes leads to difficulties with growing and maintaining crops and raising livestock. Overall, as altitude rises, the quality of the available nutritional base goes down, which is correlated to a lack of the nutrients necessary to ensure proper physiological growth and development in humans. Thus, even though individuals may be able to develop and grow within high-altitude environments, they may not reach their full genetically mediated growth potential as they would in a lower-altitude environment.
Not all developmental adjustments are linked to environmental pressures such as climate or altitude; rather, some of these adjustments are correlated to sociocultural or behavioral practices. Some of these adjustments may affect the physiological appearance of an individual when they are practiced consistently during the development and growth phases.
Sudden infant death syndrome (SIDS) has no definitive cause; however, the American Academy of Pediatrics published a report in 1992 linking SIDS to infants (under the age of one) sleeping on their stomachs. The “Back to Sleep” campaign championed by the American Academy of Pediatrics helped educate members of the medical community as well as the public that the best sleep position for infants is on their backs (American Academy of Pediatrics 2000).
Placing infants on their backs to sleep has led to decreased infant mortality (death) rates due to SIDS; however, it has led to an unintended consequence: infant cranial deformation. The cranial deformations experienced by infants who sleep solely on their back tend to manifest in one of two forms: brachycephaly and plagiocephaly (Roby et al. 2012; Figure 15.8). With positional brachycephaly, the back of the infant’s head appears rather uniformly flattened due to repetitive contact with a flat surface, such as a crib mattress or car seat back. In cases of positional plagiocephaly, the back of the infant’s head appears asymmetrically flattened. This asymmetry is typically due to an uneven distribution of mechanical forces resulting from the manner in which the infant’s head is in contact with a flat surface. The forms of cranial deformation resulting from sleep positioning do not affect the infant’s brain development. For many individuals, the appearance of the deformation is minimized during later development. Still, some individuals will maintain the pattern of cranial deformation acquired during their infancy throughout their lives. The unintentional cranial deformation resulting from placing infants on their backs to sleep as a means of preventing SIDS-related deaths is a physiological indicator of a behavioral adjustment.
Adaptations
As we have just explored, survival and reproduction at high altitudes present numerous physiological challenges for most humans. The behavioral, acclimatory, and developmental adjustments discussed above are all related to the phenotypic plasticity of the individual; however, most adjustments are temporary in nature and they affect a single individual rather than all individuals within a population. But what if the physiological changes were permanent? What if they affected all members of a population rather than just a single individual? The long-term, microevolutionary (i.e., genetic) changes that occur within a population in response to an environmental stressor are referred to as an adaptation. From an evolutionary standpoint, the term adaptation refers to a phenotypic trait (i.e., physiological/morphological feature or behavior) that has been acted upon by natural selection processes to increase a species’ ability to survive and reproduce within a specific environment. Within the field of physiology, the term adaptation refers to traits that serve to restore homeostasis. The physiology-based interpretation of adaptations presumes that all traits serve a purpose and that all adaptations are beneficial in nature; however, this may be a fallacy, since some traits may be present without clear evidence as to their purpose. As such, during the following discussion of various forms of adaptations in human populations, we will focus our attention on phenotypic traits with an evidence-based purpose.
Adaptation: Altitudinal Adaptation
As mentioned in the previous section, there is genomic research supporting the evolutionary selection of certain phenotypes and their corresponding genotypes within indigenous high-altitude populations across the globe. The following discussion focuses on two high-altitude indigenous populations from Tibet and Ethiopia (Figure 15.9). Although these populations share many common genetic traits based on relatively similar evolutionary histories influenced by similar environmental stressors, there is support for local genetically based adaptation as well, based on different genes being acted upon by environmental stressors that may be unique to Tibet and Ethiopia (Bigham 2016).
Tibetan populations have resided in the Tibetan Plateau and Himalayan Mountain regions at elevations exceeding 4,000 masl (13,100 fasl) for at least the past 7,400 years (Meyer et al. 2017). There is evidence of a genetic exchange event involving Tibetan populations and Denisovans around 48,700 years ago, which introduced a haplogroup involving mutations of the EPAS1 gene (Zhang et al. 2021). The EPAS1 is involved in the regulation of erythrocytes and hemoglobin. For individuals originating in lower-altitude environments, EPAS1 stimulates increased erythrocyte production in high-altitude environments as a temporary acclimatory adjustment. For indigenous high-altitude populations of Tibet, the EPAS1 gene mutation introduced by Denisovan introgression inhibits increased erythrocyte production, which reduces potential negative effects (e.g., stroke or heart attack) associated with long-term high levels of erythrocyte production (Gray et al. 2022; Zhang et al. 2021). The erythrocyte count of high-altitude Tibetans with the EPAS1 point mutation is about the same as for individuals residing at sea level.
Populations indigenous to the Semien Plateau of Ethiopia, such as the Oromo and Amhara, share a similar but not identical EPAS1 point mutation with the Tibetan population (Bigham 2016); however, there is no indication that this mutation was derived from Denisovan introgression. The EPAS1 mutations occurred independently from each other; however, their effects are still similar in that they permit the Tibetan and Ethiopian populations to survive at high altitudes. Not all adaptations are related to life in high-altitude environments, however. In the following sections, we will address two more general examples of adaptation in human populations: variations in skin color and differences in body build.
Adaptation: Skin Tone Basics
When you think about your own skin tone and compare it to members of your family, do you all possess exactly the same shade? Are some members of your family darker than others? What about your friends? Your classmates? Skin tone occurs along a continuum, which is a reflection of the complex evolutionary history of our species. The expression of skin tone is regulated primarily by melanin and hemoglobin. Melanin is a dark brown-black pigment that is produced by the oxidation of certain amino acids (e.g., tyrosine, cysteine, phenylalanine) in melanocytes. Melanocytes are specialized cells located in the base layer (stratum basale) of the skin’s epidermis as well as several other areas within the body (Figure 15.10). Within the melanocytes, melanin is produced in the special organelle called a melanosome. Melanosomes serve as sites for the synthesis, storage, and transportation of melanin. Melanosomes transport the melanin particles through cellular projections to epidermal skin cells (keratinocytes) as well as to the base of the growing hair root. In the eye, however, melanin particles produced by the melanosomes remain present within the iris and are not transported beyond their origin location. The two main forms of melanin related to skin, hair, and eye color are eumelanin and pheomelanin. All humans contain both eumelanin and pheomelanin within their bodies; however, the relative expression of these two forms of melanin determines an individual’s overall coloring. Eumelanin is a brown-to-black colored melanin particle while pheomelanin is more pink-to-red colored. Individuals with darker skin or hair color have a greater expression of eumelanin than those with lighter-colored skin and blonde or red hair.
Adaptation: Melanogenesis
Although all humans have approximately the same number of melanocytes within their epidermis, the production of melanin by these melanocytes varies. There are two forms of melanogenesis (the process through which melanocytes generate melanin): basal and activated. As discussed previously, the expression of eumelanin and pheomelanin by the melanocytes is genetically regulated through the expression of specific receptors (e.g., MC1R) or other melanocyte components (e.g., MFSD12). Basal melanogenesis is dependent upon an individual’s inherent genetic composition and is not influenced by external factors. Activated melanogenesis occurs in response to ultraviolet radiation (UV) exposure, specifically UV-B (short UV wave) exposure. Increased melanogenesis in response to UV-B exposure serves to provide protection to the skin’s innermost layer called the hypodermis, which lies below the epidermis and dermis (Figure 15.11). Melanin in the skin, specifically eumelanin, effectively absorbs UV-B radiation from light—meaning that it will not reach the hypodermal layer. This effect is often more apparent during periods of the year when people tend to be outside more and the weather is warmer, which leads to most donning fewer protective garments. The exposure of skin to sunlight is, of course, culturally mediated with some cultures encouraging the covering of skin at all times.
As previously noted in this chapter, hemoglobin is an iron-rich protein that binds with oxygen in the bloodstream. For individuals with lighter-colored skin, blood vessels near the surface of the skin and the hemoglobin contained within those vessels is more apparent than in individuals with darker skin. The visible presence of hemoglobin coupled with the pink-to-red tone of the pheomelanin leads to lighter-skinned individuals having a pale pink skin tone. Individuals with lighter skin more readily absorb UV radiation as their basal melanin expression is directed more toward the production of pheomelanin than eumelanin. But why are there so many variations in skin tone in humans? To answer this question, we now turn toward an exploration of an evolutionary-based adaptation of skin tone as a function of the environment.
Adaptation: Evolutionary Basis for Skin Tone Variation
Skin cancer is a significant concern for many individuals with light skin tone as the cumulative exposure of the epidermis and underlying skin tissues to UV radiation may result in the development of abnormal cells within those tissues, leading to malignancies. Although darker-skinned individuals are at risk for skin cancer as well, they are less likely to develop it due to increased levels of melanin, specifically eumelanin, in their skin. Even though skin cancer is a serious health concern for some individuals, most skin cancers occur in the postreproductive years; therefore, it is improbable that evolutionary forces favoring varying melanin expression levels are related to a selective pressure to avoid such cancers. Furthermore, if avoiding skin cancer were the primary factor driving the evolution of various skin tones, then it reasons that everyone would have the most significant expression of eumelanin possible. So, why do we have different skin tones (Figure 15.12)?
The term cline (introduced in Chapter 13) refers to the continuum or spectrum of gradations (i.e., levels or degrees) from one extreme to another. With respect to skin tone, the various tonal shades occur clinally with darker skin being more prevalent near the equator and gradually decreasing in tone (i.e., decreased melanin production) in more distant latitudes. For individuals who are indigenous to equatorial regions, the increased levels of melanin within their skin provides them with a measure of protection against both sunburn and sunstroke because the melanin is more reflective of UV radiation than hemoglobin. In cases of severe sunburn, eccrine glands are affected, resulting in an individual’s ability to sweat being compromised. As sweat is the body’s most effective means of reducing its core temperature to maintain homeostasis, damage to the eccrine glands may lead to numerous physiological issues related to heat that may ultimately result in death.
Even though avoiding severe sunburn and sunstroke is of great importance to individuals within equatorial regions, this is likely not the primary factor driving the evolutionary selection of darker skin within these regions. It has been proposed that UV radiation’s destruction of folic acid, which is a form of B-complex vitamin, may have led to the selection of darker skin in equatorial regions. For pregnant people, low levels of folic acid within the body during gestation may lead to defects in the formation of the brain and spinal cord of the fetus. This condition, which is referred to as spina bifida (Figure 15.13), often significantly reduces an infant’s chances of survival without medical intervention. In people producing sperm, low levels of folic acid within the body reduce sperm quantity and quality. Thus, in geographic regions with high UV radiation levels (i.e., equatorial regions), there appears to be an evolutionarily driven correlation between darker skin and fertility.
If darker skin tone is potentially correlated to more successful reproduction, then why do lighter shades of skin exist? One hypothesis is that there is a relationship between lighter skin tone and vitamin D synthesis within the body. When skin is exposed to the UV-B radiation waves in sunlight, a series of chemical reactions occur within the epidermis leading to the production of vitamin D3, which is a fat-soluble vitamin that assists the body with absorbing calcium and phosphorus in the small intestine. These nutrients are among those that are critical for the proper growth and maintenance of bone tissue within the body. In the absence of adequate minerals, particularly calcium, bone structure and strength will be compromised, leading to the development of rickets during the growth phase. Rickets is a disease affecting children during their growth phase. It is characterized by inadequately calcified bones that are softer and more flexible than normal. Individuals with rickets will develop a true bowing of their legs, which may affect their mobility (Figure 15.14). In addition, deformation of pelvic bones in people who may become pregnant may occur as a result of rickets, leading to complications with reproduction. In adults, a deficiency in vitamin D3 will often result in osteomalacia, which is a general softening of the bones due to inadequate mineralization. As noted, a variety of maladies may occur due to the inadequate production or absorption of vitamin D3, as well as the destruction of folate within the human body. Therefore, from an evolutionary perspective, natural selection should favor a skin tone that is best suited to a given environment.
In general, the trend related to lighter skin pigmentation further from the equator follows a principle called Gloger’s Rule. This rule states that within the same species of mammals the more heavily pigmented individuals tend to originate near the equator while lighter-pigmented members of the species will be found in regions further from the equator. Gloger’s Rule applies latitudinally; however, it does not appear to hold for certain human populations near the poles. Specifically, it does not apply to the Inuit people (Figure 15.15), who are indigenous to regions near the North Pole and currently reside in portions of Canada, Greenland, Alaska, and Denmark. The Inuit have a darker skin tone that would not be anticipated under the provisions of Gloger’s Rule. The high reflectivity of light off of snow and ice, which is common in polar regions, necessitates the darker skin tone of these individuals to prevent folic acid degradation just as it does for individuals within equatorial regions. The consumption of vitamin D–rich foods, such as raw fish, permits the Inuit to reside at high latitudes with darker skin tone while preventing rickets.
Adaptation: Shape and Size Variations
In addition to natural selection playing a role in the determination of melanin expression, it plays a significant role in the determination of the shape and size of the human body. As previously discussed, the most significant thermodynamic mechanism of heat loss from the body is radiation. At temperatures below 20℃ (68℉), the human body loses around 65% of its heat to radiative processes; however, the efficiency of radiation is correlated to the overall body shape and size of the individual. There is a direct correlation between the ratio of an object’s surface area to mass and the amount of heat that may be lost through radiation. For example, two objects of identical composition and mass are heated to the same temperature. One object is a cube and the other is a sphere. Which object will cool the fastest? Geometrically, a sphere has the smallest surface area per unit mass of any three-dimensional object, so the sphere will cool more slowly than the cube. In other words, the smaller the ratio of the surface area to mass an object has, the more it will retain heat. With respect to the cube in our example, mass increases by the cube, but surface area may increase only by the square, so size will affect the mass to surface area ratio. This, in general, holds true for humans, as well.
In regions where temperatures are consistently cold, the body shape and size of individuals indigenous to the area tend to be more compact. These individuals have a relatively higher body mass to surface area (i.e., skin) than their counterparts from equatorial regions where the average temperatures are considerably warmer. Individuals from hot climates, such as the Fulani (Figure 15.16a) of West Africa, have limbs that are considerably longer than those of individuals from cold climates, such as the Inuit of Greenland (Figure 15.16b). Evolutionarily, the longer limbs of individuals from equatorial regions (e.g., the Fulani) provide a greater surface area (i.e., lower body mass to surface area ratio) for the dissipation of heat through radiative processes. In contrast, the relatively short limbs of Arctic-dwelling people, such as the Inuit, allows for the retention of heat because there is a decreased surface area through which heat may radiate away from the body.
As described above, there are certain trends related to the general shape and size of human bodies in relation to the thermal conditions. To better describe these trends, we turn to a couple of general principles that are applicable to a variety of species beyond humans. Bergmann’s Rule predicts that as average environmental temperature decreases, populations are expected to exhibit an increase in weight and a decrease in surface area (Figure 15.17a). Also, within the same species of homeothermic animals, the relative length of projecting body parts (e.g., nose, ears, and limbs) increases in relation to the average environmental temperature (Figure 15.17b). This principle, referred to as Allen’s Rule, notes that longer, thinner limbs are advantageous for the radiation of excess heat in hot environments and shorter, stockier limbs assist with the preservation of body heat in cold climates. A measure of the crural index (crural index = tibia length ÷ femur length) of individuals from various human populations provides support for Allen’s Rule since this value is lower in individuals from colder climates than it is for those from hot climates. The crural indices for human populations vary directly with temperature, so individuals with higher crural index values are generally from regions with a warmer average environmental temperature. Conversely, the crural indices are lower for individuals from regions where there are colder average temperatures.
Nasal shape and size (Figure 15.18) is another physiological feature affected by our ancestors’ environments. The selective role of climate in determining human nasal variation is typically approached by dividing climates into four adaptive zones: hot-dry, hot-wet, cold-dry, and cold-wet (Maddux et al. 2016). A principal role of the nasal cavity is to condition (i.e., warm and humidify) ambient air prior to its reaching the lungs. Given this function of the nasal cavity, it is anticipated that different nasal shapes and sizes will be related to varying environments. In cold-dry climates, an individual’s nasal cavity must provide humidification and warmth to the dry air when breathing in through the nose (Noback et al. 2011). Also, in that type of climate, the nasal cavity must conserve moisture and minimize heat loss during when the individual exhales through the nose (Noback et al. 2011). From a physiological stress perspective, this is a stressful event.
Conversely, in hot-wet environments, there is no need for the nasal cavity to provide additional moisture to the inhaled air nor is there a need to warm the air or to preserve heat within the nasal cavity (Noback et al. 2011). So, in hot-wet climates, the body is under less physiological stress related to the inhalation of ambient air than in cold-dry climates. As with most human morphological elements, the shape and size of the nasal cavity occurs along a cline. Due to the environmental stressors of cold-dry environments requiring the humidification and warming of air through the nasal cavity, individuals indigenous to such environments tend to have taller (longer) noses with a reduced nasal entrance (nostril opening) size (Noback et al. 2011). This general shape is referred to as leptorrhine, and it allows for a larger surface area within the nasal cavity itself for the air to be warmed and humidified prior to entering the lungs (Maddux et al. 2016). In addition, the relatively small nasal entrance of leptorrhine noses serves as a means of conserving moisture and heat (Noback et al. 2011). Individuals indigenous to hot-wet climates tend to have platyrrhine nasal shapes, which are shorter with broader nasal entrances (Maddux et al. 2016). Since individuals in hot-wet climates do not need to humidify and warm the air entering the nose, their nasal tract is shorter and the nasal entrance wider to permit the effective cooling of the nasal cavity during respiratory processes.
Adaptation: Infectious Disease
Throughout our evolutionary journey, humans have been exposed to numerous infectious diseases. In the following section, we will explore some of the evolutionary-based adaptations that have occurred in certain populations in response to the stressors presented by select infectious diseases. One of the primary examples of natural selection processes acting on the human genome in response to the presence of an infectious disease is the case of the relationship between the sickle-cell anemia trait and malaria, introduced in Chapter 4.
Malaria is a zoonotic disease (an infectious disease transmitted between animals and humans; it is covered in more detail in Chapter 16). It is caused by the spread of the parasitic protozoa from the genus Plasmodium (Figure 15.19). These unicellular, eukaryotic protozoa are transmitted through the bite of a female Anopheles mosquito. During the bite process, the protozoan parasites present within an infected mosquito’s saliva enter a host’s bloodstream where they are transported to the liver. Within the liver, the parasites multiply and are eventually released into the bloodstream, where they infect erythrocytes. Once inside the erythrocytes, the parasites reproduce until they exceed the cell’s storage capacity, causing it to burst and release the parasites into the bloodstream once again. This replication cycle continues as long as there are viable erythrocytes within the host to infect.
General complications from malaria infections include the following: enlargement of the spleen (due to destruction of infected erythrocytes); lower number of thrombocytes (also called platelets, required for coagulation/clotting of blood); high levels of bilirubin (a byproduct of hemoglobin breakdown in the liver) in the blood; jaundice (yellowing of the skin and eyes due to increased blood bilirubin levels); fever; vomiting; retinal (eye) damage; and convulsions (seizures). In 2020, there were 241 million cases of malaria reported globally, with 95% of those cases originating in Africa (World Health Organization 2021). In sub-Saharan Africa, where incidents of malaria are the highest in the world, 125 million pregnancies are affected by malaria, resulting in 200,000 infant deaths (Hartman, Rogerson, and Fischer 2013). Pregnant people who become infected during the gestational process are more likely to have low-birthweight infants due to prematurity or growth restriction inside the uterus (Hartman, Rogerson, and Fischer 2013). After birth, infants born to malaria-infected pregnant people are more likely to develop infantile anemia (low red-blood cell counts), a malaria infection that is not related to the maternal malarial infection, and they are more likely to die than infants born to non-malaria-infected pregnant people (Hartman, Rogerson, and Fischer 2013).
For children and adolescents whose brains are still developing, there is a risk of cognitive (intellectual) impairment associated with some forms of malaria infections (Fernando, Rodrigo, and Rajapakse 2010). Given the relatively high rates of morbidity (disease) and mortality (number of deaths) associated with malaria, it is plausible that this disease may have served as a selective pressure during human evolution. Support for natural selection related to malaria resistance is related to genetic mutations associated with sickle cell, thalassemia, glucose-6-phosphate dehydrogenase (G6PD) deficiency, and the absence of certain antigens (molecules capable of inducing an immune response from the host) on erythrocytes. For the purposes of this text, we will focus our discussion on the relationship between sickle cell disease and malaria.
Sickle cell disease is a group of genetically inherited blood disorders characterized by an abnormality in the shape of the hemoglobin within erythrocytes. It is important to note that there are multiple variants of hemoglobin, including, but not limited to the following: A, D, C, E, F, H, S, Barts, Portland, Hope, Pisa, and Hopkins. Each of these variants of hemoglobin may result in various conditions within the body; however, for the following explanation we will focus solely on variants A and S.
Individuals who inherit a mutated gene (hemoglobin with a sickled erythrocyte variety, HbS) on chromosome 11 from both parents will develop sickle cell anemia, which is the most severe form of the sickle cell disease family (Figure 15.20). The genotype of an individual with sickle cell anemia is HbSS; whereas, an individual without sickle cell alleles has a genotype of HbAA representing two normal adult hemoglobin type A variants. Manifestations of sickle cell anemia (HbSS) range from mild to severe, with some of the more common symptoms being anemia, blood clots, organ failure, chest pain, fever, and low blood-oxygen levels. In high-income countries with advanced medical care, the median life expectancy of an HbSS individual is around 60 years; however, in low-income countries where advanced medical care is scarce, as many as 90% of children with sickle cell disease perish before the age of five (Longo et al. 2017).
Considering that advanced medical care was not available during much of human evolutionary history, it stands to reason that the majority of individuals with the HbSS genotype died before the age of reproduction. If that is the case though, why do we still have the HbS variant present in modern populations? As covered earlier in this textbook, the genotype of an individual is composed of genes from both biological parents. In the case of an individual with an HbSS genotype, the sickle cell allele (HbS) was inherited from each of the parents. For individuals with the heterozygous genotype of HbSA, they have inherited both a sickle cell allele (HbS) and a normal hemoglobin allele (HbA). Heterozygous (HbSA) individuals who reside in regions where malaria is endemic may have a selective advantage. They will experience a sickling of some, but not all, of their erythrocytes. As discussed in the following paragraph, HbSA heterozygous individuals are less likely to die from malaria infections than their HbAA counterparts. Unlike an individual with the HbSS genotype, someone with HbSA may experience some of the symptoms listed above; however, they are generally less severe.
As noted earlier, the mechanism through which Plasmodium protozoan parasites replicate involves human erythrocyte cells. However, due to their sickled shape, as well as the presence of an abnormally shaped protein within the cell, the parasites are unable to replicate effectively in the erythrocyte cells coded for by the HbS allele (Cyrklaff et al. 2011). An individual who has an HbSA genotype and an active malaria infection will become ill with the disease to a lesser extent than someone with an HbAA genotype, which increases their chances of survival. Although normal erythrocytes (regulated by the HbA allele) allow for parasite replication, they are not able to replicate in HbS erythrocytes of the heterozygote. So, individuals with the HbSA genotype are more likely to survive a malaria infection than an individual who is HbAA. Although individuals with the HbSA genotype may endure some physiological complications related to the sickling of some of their erythrocytes, their morbidity and mortality rates are lower than they are for HbSS members of the population. The majority of individuals who are heterozygous or homozygous for the HbS trait have ancestors who originated in sub-Saharan Africa, India, Saudi Arabia, and regions in South and Central America, the Mediterranean (Turkey, Greece, and Italy), and the Caribbean (Centers for Disease Control and Prevention 2017; Figure 15.21).
With respect to the history of these regions, during the early phases of settlement horticulture was the primary method of crop cultivation. Typically performed on a small scale, horticulture is based on manual labor and relatively simple hand tools rather than the use of draft animals or irrigation technologies. Common in horticulture is swidden, or the cutting and burning of plants in woodland and grassland regions. The swidden is the prepared field that results following a slash-and-burn episode. This practice fundamentally alters the soil chemistry, removes plants that provide shade, and increases the areas where water may pool. This anthropogenically altered landscape provides the perfect breeding ground for the Anopheles mosquito, as it prefers warm, stagnant pools of water (Figure 15.22).
Although swidden agriculture was historically practiced across the globe, it became most problematic in the regions where the Anopheles mosquito is endemic. These areas have the highest incidence rates of malaria infection. Over time, the presence of the Anopheles mosquito and the Plasmodium parasite that it transmitted acted as a selective pressure, particularly in regions where swidden agricultural practices were common, toward the selection of individuals with some modicum of resistance against the infection. In these regions, HbSS and HbSA individuals would have been more likely to survive and reproduce successfully. Although individuals and populations are far more mobile now than they have been throughout much of history, there are still regions where we can see higher rates of malaria infection as well as greater numbers of individuals with the HbS erythrocyte variant. The relationship between malaria and the selective pressure for the HbS variant is one of the most prominent examples of natural selection in the human species within recent evolutionary history.
Adaptation: Lactase Persistence
With the case of sickled erythrocytes and their resistance to infection by malaria parasites, there is strong support for a cause-and-effect-style relationship linked to natural selection. Although somewhat less apparent, there is a correlation between lactase persistence and environmental challenges. Lactase-phlorizin hydrolase (LPH) is an enzyme that is primarily produced in the small intestine and permits the proper digestion of lactose, a disaccharide (composed of two simple sugars: glucose and galactose) found in the milk of mammals. Most humans will experience a decrease in the expression of LPH following weaning, leading to an inability to properly digest lactose. Generally, LPH production decreases between the ages of two and five and is completely absent by the age of nine (Dzialanski et al. 2016). For these individuals, the ingestion of lactose may lead to a wide variety of gastrointestinal ailments, including abdominal bloating, increased gas, and diarrhea. Although the bloating and gas are unpleasant, the diarrhea caused by a failure to properly digest lactose can be life-threatening if severe enough due to the dehydration it can cause. Some humans, however, are able to produce LPH far beyond the weaning period.
Individuals who continue to produce LPH have what is referred to as the lactase persistence trait. The lactase persistence trait is encoded for a gene called LCT, which is located on human chromosome 2 (Ranciaro et al. 2014; see also Chapter 3). From an evolutionary and historical perspective, this trait is most commonly linked to cultures that have practiced cattle domestication (Figure 15.23). For individuals in those cultures, the continued expression of LPH may have provided a selective advantage. During periods of environmental stress, such as a drought, if an individual is capable of successfully digesting cow’s milk, they have a higher chance of survival than someone who suffers from diarrhea-linked dehydration due to a lack of LPH. Although the frequency of the lactase persistence trait is relatively low among African agriculturalists, it is high among pastoralist populations that are traditionally associated with cattle domestication, such as the Tutsi and Fulani, who have frequencies of 90% and 50%, respectively (Tishkoff et al. 2007).
Cattle domestication began around 11,000 years ago in Europe (Beja-Pereira et al. 2006) and 7,500 to 9,000 years ago in the Middle East and North Africa (Tishkoff et al. 2007). Based on human genomic studies, it is estimated that the mutation for the lactase persistence trait occurred around 2,000 to 20,000 years ago for European populations (Tishkoff et al. 2007). For African populations, the lactase persistence trait emerged approximately 1,200 to 23,000 years ago (Gerbault et al. 2011). This begs the question: Is this mutation the same for both populations? It appears that the emergence of the lactase persistence mutation in non-European populations, specifically those in East Africa (e.g., Tutsi and Fulani), is a case of convergent evolution. With convergent evolution events, a similar mutation may occur in species of different lineages through independent evolutionary processes. Based on our current understanding of the genetic mutation pathways for the lactase persistence trait in European and African populations, these mutations are not representative of a shared lineage. In other words, just because a person of European origin and a person of African origin can each digest milk due to the presence of the lactase-persistence trait in their genotypes, it does not mean that these two individuals inherited it due to shared common ancestry.
Is it possible that the convergent evolution of similar lactase-persistence traits in disparate populations is merely a product of genetic drift? Or is there evidence for natural selection? Even though 23,000 years may seem like a long time, it is but a blink of the proverbial evolutionary eye. From the perspective of human evolutionary pathways, mutations related to the LCT gene have occurred relatively recently. Similar genetic changes in multiple populations through genetic drift processes, which are relatively slow and directionless, fail to accumulate as rapidly as lactase-persistence traits (Gerbault et al. 2011). The widespread accumulation of these traits in a relatively short period of time supports the notion that an underlying selective pressure must be driving this form of human evolution. Although to date no definitive factors have been firmly identified, it is thought that environmental pressures are likely to credit for the rapid accumulation of the lactase-persistence trait in multiple human populations through convergent evolutionary pathways.
Special Topic: Skin Tone Genetic Regulation
The melanocortin 1 receptor (MC1R) gene acts to control which types of melanin (eumelanin or pheomelanin) are produced by melanocytes. The MC1R receptor is located on the surface of the melanocyte cells (Quillen et al. 2018). Activation of the MC1R receptors may occur through exposure to specific environmental stimuli or due to underlying genetic processes. Inactive or blocked MC1R receptors result in melanocytes producing pheomelanin. If the MC1R gene receptors are activated, then the melanocytes will produce eumelanin. Thus, individuals with activated MC1R receptors tend to have darker-pigmented skin and hair than individuals with inactive or blocked receptors.
The alleles of another gene, the major facilitator, superfamily domain-containing protein 12 (MFSD12) gene, affect the expression of melanocytes in a different way than the MC1R gene. Instead of affecting the activation of melanocyte receptors, the MFSD12 alleles indirectly affect the membranes of melanocyte lysosomes (Quillen et al. 2018). The melanocyte’s lysosomes are organelles containing digestive enzymes, which ultimately correlate to varying degrees of pigmentation in humans. Variations in the membranes of the melanocyte lysosomes ultimately correlate to differing degrees of pigmentation in humans.
Ancestral MFSD12 allele variants are present in European and East Asian populations and are associated with lighter pigmentation of the skin (Crawford et al. 2017; Quillen et al. 2018). In addition, this ancestral variant is also associated with Tanzanian, San, and Ethiopian populations of Afro-Asiatic ancestry (Crawford et al. 2017; Quillen et al. 2018). In contrast, the more derived (i.e., more recent) allele variants that are linked to darker skin tones are more commonly present in East African populations, particularly those of Nilo-Saharan descent (Crawford et al. 2017; Quillen et al. 2018). The notion that ancestral alleles of MFSD12 are associated with lighter skin pigmentation is in opposition to the commonly accepted idea that our pigmentation was likely darker throughout early human evolution (Crawford et al. 2017; Quillen et al. 2018). Due to the complexity of the human genome, MFSD12 and MC1R are but two examples of alleles affecting human skin tone. Furthermore, there is genetic evidence suggesting that certain genomic variants associated with both darker and lighter skin color have been subject to directional selection processes for as long as 600,000 years, which far exceeds the evolutionary span of Homo sapiens sapiens (Crawford et al. 2017; Quillen et al. 2018).
Human Variation: Our Story Continues
From the time that the first of our species left Africa, we have had to adjust and adapt to numerous environmental challenges. The remarkable ability of human beings to maintain homeostasis through a combination of both nongenetic (adjustments) and genetic (adaptations) means has allowed us to occupy a remarkable variety of environments, from high-altitude mountainous regions to the tropics near the equator. From adding piquant, pungent spices to our foods as a means of inhibiting food-borne illnesses due to bacterial growth to donning garments specially suited to local climates, behavioral adjustments have provided us with a nongenetic means of coping with obstacles to our health and well-being. Acclimatory adjustments, such as sweating when we are warm in an attempt to regulate our body temperature or experiencing increased breathing rates as a means of increasing blood oxygen levels in regions where the partial pressure of oxygen is low, have been instrumental in our survival with respect to thermal and altitudinal environmental challenges. For some individuals, developmental adjustments that were acquired during their development and growth phases (e.g., increased heart and lung capacities for individuals from high-altitude regions) provide them with a form of physiological advantage not possible for someone who ventures to such an environmentally challenging region as an adult. Genetically mediated adaptations, such as variations in the pigmentation of our skin, have ensured our evolutionary fitness across all latitudes.
Will the human species continue to adjust and adapt to new environmental challenges in the future? If past performance is any measure of future expectations, then the human story will continue as long as we do not alter our environment to the point that the plasticity of our behavior, physiological, and morphological boundaries is exceeded. In the following chapters, you will explore additional information about our saga as a species. From the concept of race as a sociocultural construct to our epidemiological history, the nuances of evolutionary-based human variation are always present and provide the basis for understanding our history and our future as a species.
Review Questions
- Detail at least two examples of how natural selection has influenced human variation. Specifically, what was the selective pressure that may have led to a preference for a specific trait and how is that trait related to an increased level of fitness?
- Why is reduced pigmentation of the skin advantageous for individuals from northern latitudes? What role does darker skin pigmentation serve for individuals near the equator? What is the relationship between skin pigmentation and fitness?
- What are some of the risks associated with pregnancy at high altitude? Compare and contrast the various genetic mutations of the indigenous Tibetan and Ethiopian high-altitude populations. In your answer, specifically address the issue of pregnancy at high altitudes.
- What is the relationship between the sickle cell mutation and the Plasmodium parasite? Would having the HbSA genotype still be advantageous in a region where such parasites are not common? Why or why not?
Key Terms
Acclimatory adjustments: Processes by which an individual organism adjusts in order to maintain homeostasis in response to environmental challenges.
Activated melanogenesis: Increase in melanin production in response to ultraviolet radiation (UV) exposure.
Adaptation: Alteration in population-level gene frequencies related to environmentally induced selective pressures; leads to a greater level of fitness for a population related to a specific environment.
Adjustment: Nongenetic-based ways in which organisms adjust to environmental stressors.
Allen’s Rule: Due to thermal adaptation, homeothermic animals have body volume-to-surface ratios that vary inversely with the average temperature of their environment. In cold climates, the anticipated ratio is high; in warm climates, it is low.
Basal melanogenesis: Genetically mediated, non-environmentally influenced base melanin level.
Behavioral adjustments: An individual’s culturally mediated responses to an environmental stressor in an effort to maintain homeostasis.
Bergmann’s Rule: For a broadly distributed monophyletic group, species and populations of smaller size tend to be found in environments with warmer climates and those of larger size tend to be found in ones that are colder.
Cline: A continuum of gradations (i.e., degrees or levels) of a specific trait.
Conduction: Mechanism of heat transfer between objects through direct contact.
Convection: Movement of heat away from a warm object to the cooler surrounding fluid (i.e., gas or liquid).
Convergent evolution: Evolutionary process whereby organisms that are not closely related independently evolve similar traits as a product of adaptation to similar evolutionary parameters.
Erythrocyte: Red blood cell; most common form of blood cell; the principle means of transporting oxygen throughout the circulatory system.
Evaporation: Mechanism of heat transfer whereby liquid is transformed into a gas, utilizing energy (e.g., heat).
Folic acid: Form of B complex vitamin necessary for proper fetal development.
Gloger’s Rule: For mammals of the same species, those with more darkly pigmented forms tend to be found closer to the equator and those with lighter forms are found in regions further from the equator.
Homeostasis: Condition of optimal functioning for an organism.
Hyperpnea: Increased depth and rate of respiration.
Hypothalamus: Small portion of the human brain responsible for body temperature regulation.
Lactase persistence: Genetic mutation permitting the continued production of lactase-phlorizin hydrolase enzyme in the small intestine past the weaning period.
Melanin: Black-brown pigment produced by melanocytes; one of the primary pigments in skin.
Melanocytes: Specialized cells that produce melanin.
Phenotypic plasticity: Ability of one genotype to produce more than one phenotype dependent on environmental conditions.
Radiation: Mechanism of heat transfer involving electromagnetic energy being emitted from an object.
Sickle cell disease: A group of genetically inherited blood disorders characterized by an abnormality in the shape of the hemoglobin within erythrocytes (red blood cells).
Stressor: Any stimulus resulting in an imbalance in an organism’s homeostatic balance.
Vasoconstriction: Narrowing of the blood vessels due to contractions of the muscular vessel walls.
Vasodilation: Dilation of the blood vessels due to relaxation of the muscular vessel walls.
For Further Exploration
Homeostasis
Baptista, Vander. 2006. “Starting Physiology: Understanding Homeostasis.” Advances in Physiology Education 30: 263–264.
Goldstein, David S., and Bruce McEwen. 2002. “Allostasis, Homeostats, and the Nature of Stress.” The International Journal on the Biology of Stress 5 (1): 55–58.
General Clinal Variation and Genetic Exchange
Delhey, Kaspar. 2019. “A Review of Gloger's Rule, an Ecogeographical Rule of Colour: Definitions, Interpretations and Evidence.” Biological Reviews 94 (4): 1294–1316.
Feng, Yuanqing, Michael A. McQuillan, and Sarah A. Tishkoff. 2021. “Evolutionary Genetics of Skin Pigmentation in African Populations.” Human Molecular Genetics 30 (R1): R88–R97.
Hu, Hao, Nayia Petousi, Gustavo Glusman, Yao Yu, Ryan Bohlender, Tsewang Tashi, Jonathan M. Downie, et al. 2017. “Evolutionary History of Tibetans Inferred from Whole-Genome Sequencing.” PLoS Genetics 13 (4): e1006675. .
Jablonski, Nina G. 2021. “Skin Color and Race.” Special issue, “Race Reconciled II: Interpreting and Communicating Biological Variation and Race in 2021,” American Journal of Physical Anthropology 175 (2): 437–447.
Pritchard, Jonathan K., Joseph K. Pickrell, and Graham Coop. 2010. “The Genetics of Human Adaptation: Hard Sweeps, Soft Sweeps, and Polygenic Adaptation.” Current Biology 20 (4): R208–R215.
Sankararaman, Sriram, Swapan Mallick, Nick Patterson, and David Reich. 2016. “The Combined Landscape of Denisovan and Neanderthal Ancestry in Present-Day Humans.” Current Biology 26 (9): 1241–1247.
Lactase Persistence
HHMI BioInteractive. 2021. “The Making of the Fittest: Got Lactase? The Co-evolution of Genes and Culture.” Accessed April 7, 2023.
Malaria and Sickle Cell Anemia
Bill and Melinda Gates Foundation. 2022. “Malaria.” Accessed April 7, 2023.
Centers for Disease Control and Prevention. 2022. “Malaria.” Accessed April 7, 2023.
HHMI BioInteractive. 2020. “The Making of the Fittest: Natural Selection in Humans.” 2020. Accessed April 7, 2023.
National Institutes of Health: National Center for Advancing Translational Sciences. “Sickle Cell Anemia.” Accessed April 7, 2023.
World Health Organization. 2022. “Malaria.” Accessed April 7, 2023.
Rickets and Bone Health
National Institutes of Health: National Center for Advancing Translational Sciences. “Rickets.” Accessed April 7, 2023.
Talmadge, D. W., and R. V. Talmadge. 2007. “Calcium Homeostasis: How Bone Solubility Relates to All Aspects of Bone Physiology.” Journal of Musculoskeletal and Neuronal Interactions 7 (2): 108–112.
Skin Color
HHMI BioInteractive. 2020. “The Biology of Skin Color.” Accessed April 7, 2023
References
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Ashley Kendell, Ph.D., California State University, Chico
Alex Perrone, M.A., M.S.N, R.N., P.H.N., Butte Community College
Colleen Milligan, Ph.D., California State University, Chico
Student contributors to this chapter: Amelia Roberts, Elyse Racicot, Emmanuelle Hunter
This chapter is a revision from "Chapter 15: Bioarchaeology and Forensic Anthropology” by Ashley Kendell, Alex Peronne, and Colleen Milligan. In Explorations: An Open Invitation to Biological Anthropology, first edition, edited by Beth Shook, Katie Nelson, Kelsie Aguilera, and Lara Braff, which is licensed under CC BY-NC 4.0.
Content Warning and Disclaimer: This chapter includes images of human remains as well as discussions centered on human skeletal analyses. All images are derived from casts, sketches, nonhuman skeletal material, as well as non-Indigenous skeletal materials curated within the CSU, Chico Human Identification Lab, and the Hartnett-Fulginiti donated skeletal collection.
Learning Objectives
- Define forensic anthropology as a subfield of biological anthropology.
- Describe the seven steps carried out during skeletal analysis.
- Outline the four major components of the biological profile.
- Contrast the four categories of trauma.
- Explain how to identify the different taphonomic agents that alter bone.
- Discuss ethical considerations for forensic anthropology.
Forensic anthropology is a subfield of biological anthropology and an applied area of anthropology. Forensic anthropologists use skeletal analysis to gain information about humans in the present or recent past, then they apply this information within a medicolegal context. This means that forensic anthropologists specifically conduct their analysis on recently deceased individuals (typically within the last 50 years) as part of investigations by law enforcement. Forensic anthropologists can assist law enforcement agencies in several different ways, including aiding in the identification of human remains whether they are complete, fragmentary, burned, scattered, or decomposed. Additionally, forensic anthropologists can help determine what happened to the deceased at or around the time of death as well as what processes acted on the body after death (e.g., whether the remains were scattered by animals, whether they were buried in the ground, or whether they remained on the surface as the soft tissue decomposed).
Many times, because of their expertise in identifying human skeletal remains, forensic anthropologists are called to help with outdoor search-and-recovery efforts, such as locating remains scattered across the surface or carefully excavating and documenting buried remains. In other cases, forensic anthropologists recover remains after natural disasters or accidents, such as fire scenes, and can help identify whether each bone belongs to a human or an animal. Forensic anthropology spans a wide scope of contexts involving the law, including incidences of mass disasters, genocide, and war crimes.
A point that can be somewhat confusing for students is that although the term forensic is included in this subfield of biological anthropology, there are many forensic techniques that are not included in the subfield. Almost exclusively, forensic anthropology deals with skeletal analysis. While this can include the comparison of antemortem (before death) and postmortem (after death) radiographs to identify whether remains belong to a specific person, or using photographic superimposition of the cranium, it does not include analyses beyond the skeleton. For example, blood-spatter analysis, DNA analysis, fingerprints, and material evidence collection do not fall under the scope of forensic anthropology.
So, what can forensic anthropologists glean from bones alone? Forensic anthropologists can address a number of questions about a human individual based on their skeletal remains. Some of those questions are as follows: How old was the person? Was the person biologically male or female? How tall was the person? What happened to the person at or around their time of death? Were they sick? The information from the skeletal analysis can then be matched with missing persons records, medical records, or dental records, aiding law enforcement agencies with identifications and investigations.
Skeletal Analysis
Forensic anthropology relies on skeletal analysis to reveal information about the deceased. The methodology and approaches outlined below are specific to the United States. Forensic anthropological methods differ depending on the country conducting an investigation. In the United States, there are typically seven steps or questions to the process:
- Is it bone?
- Is it human?
- Is it modern or archeological?
- How many individuals are present or what is the minimum number of individuals (MNI)?
- Who is it?
- Is there evidence of trauma before or around the time of death?
- What happened to the remains after death?
Is It Bone?
One of the most important steps in any skeletal analysis starts with determining whether or not material suspected to be bone is in fact bone. Though it goes without saying that a forensic anthropologist would only carry out analysis on bone, this step is not always straightforward. Whole bones are relatively easy to identify, but determining whether or not something is bone becomes more challenging once it becomes fragmentary. As an example, in high heat such as that seen on fire scenes, bone can break into pieces. During a house fire with fatalities, firefighters watered down the burning home. After the fire was extinguished, the sheetrock (used to construct the walls of the home) was drenched and crumbled. The crumbled sheetrock was similar in color and form to burned, fragmented bone, therefore mistakable for human remains (Figure 16.1). Forensic anthropologists on scene were able to separate the bones from the construction material, helping to confirm the presence of bone and hence the presence of individual victims of the fire. In this case, forensic anthropologists were able to recognize the anatomical and layered structure of bone and were able to distinguish it from the uniform and unlayered structure of sheetrock.
As demonstrated by the example above, both the macrostructure (visible with the naked eye) and microstructure (visible with a microscope) of bone are helpful in bone identification. Bones are organs in the body made up of connective tissue. The connective tissue is hardened by a mineral deposition, which is why bone is rigid in comparison to other connective tissues such as cartilage (Tersigni-Tarrant and Langley 2017, 82–83; White and Folkens 2005, 31). In a living body, the mineralized tissue does not make up the only component of bone—there are also blood, bone marrow, cartilage, and other types of tissues. However, in dry bone, two distinct layers of the bone are the most helpful for identification. The outer layer is made up of densely arranged osseous (bone) tissue called compact (cortical) bone. The inner layer is composed of much more loosely organized, porous bone tissue whose appearance resembles that of a sponge, hence the name spongy (trabecular) bone. Knowing that most bone contains both layers helps with the macroscopic identification of bone (Figures 16.2, 16.3). For example, a piece of coconut shell might look a lot like a fragment of a human skull bone. However, closer inspection will demonstrate that coconut shell only has one very dense layer, while bone has both the compact and spongy layers.
The microscopic identification of bone relies on knowledge of osteons, or bone cells (Figure 16.4). Under magnification, bone cells are visible in the outer, compact layer of bone. The bone cells are arranged in a concentric pattern around blood vessels for blood supply. The specific shape of the cells can help differentiate, for example, a small piece of PVC (white plastic) pipe from a human bone fragment (Figure 16.5).
Is It Human?
Once it has been determined that an object is bone, the next logical step is to identify whether the bone belongs to a human or an animal. Forensic anthropologists are faced with this question in everyday practice because human versus nonhuman bone identification is one of the most frequent requests they receive from law enforcement agencies.
There are many different ways to distinguish human versus nonhuman bone. The morphology (the shape/form) of human bone is a good place for students to start. Identifying the 206 bones in the adult human skeleton and each bone’s distinguishing features (muscle attachment sites, openings and grooves for nerves and blood vessels, etc.) is fundamental to skeletal analysis.
Nevertheless, there are many animal bones and human bones that look similar. For example, the declawed skeleton of a bear paw looks a lot like a human hand, pig molars appear similar to human molars, and some smaller animal bones might be mistaken for those of an infant. To add to the confusion, fragmentary bone may be even more difficult to identify as human or nonhuman. However, several major differences between human and nonhuman vertebrate bone help distinguish the two.
Forensic anthropologists pay special attention to the density of the outer, compact layer of bone in both the cranium and in the long bones. Human cranial bone has three distinctive layers. The spongy bone is sandwiched between the outer (ectocranial) and inner (endocranial) compact layers. In most other mammals, the distinction between the spongy and compact layers is not always so definite. Secondly, the compact layer in nonhuman mammal long bones can be much thicker than observed in human bone. Due to the increased density of the compact layer, nonhuman bone tends to be heavier than human bone (Figure 16.6).
The size of a bone can also help determine whether it belongs to a human. Adult human bones are larger than subadult or infant bones. However, another major difference between human adult bones and those of a young individual or infant human can be attributed to development and growth of the epiphyses (ends of the bone). The epiphyses of human subadult bones are not fused to the shaft (Figure 16.7). Therefore, if a bone is small and it is suspected to belong to a human subadult or infant, the epiphyses would not be fused. Many small animal bones appear very similar in form compared to adult human bones, but they are much too small to belong to an adult human. Yet they can be eliminated as subadult or infant bones if the epiphyses are fused to the shaft.
Is It Modern or Archaeological?
Forensic anthropologists work with modern cases that fall within the scope of law enforcement investigations. Accordingly, it is important to determine whether discovered human remains are archaeological or forensic in nature. Human remains that are historic are considered archeaological. The scientific study of human remains from archaeological sites is called bioarchaeology.
Dig Deeper: Bioarchaeology
For readers who are interested in the sister subfield of bioarchaeology, which studies human remains and material culture from the past, please refer to chapter 8 of Bioarchaeology: Interpreting Human Behavior from Skeletal Remains, in TRACES: An Open Invitation to Archaeology (Blatt, Michael, and Bright forthcoming).
A forensic anthropologist should begin their analysis by reviewing the context in which the remains were discovered. This will help them understand a great deal about the remains, including determining whether they are archaeological or forensic in nature as well as considering legal and ethical issues associated with the collection, analysis, and storage of human remains (see “Ethics and Human Rights” section of this chapter for more information).
The “context” refers to the relationship the remains have to the immediate area in which they were found. This includes the specific place where the remains were found, the soil or other organic matter immediately surrounding the remains, and any other objects or artifacts in close proximity to the body. For example, imagine that a set of remains has been located during a house renovation. The remains are discovered below the foundation. Do the remains belong to a murder victim? Or was the house built on top of an ancient burial ground? Observing information from the surroundings can help determine whether the remains are archaeological or modern. How long ago was the foundation of the house erected? Are there artifacts in close proximity to the body, such as clothing or stone tools? These are questions about the surroundings that will help determine the relative age of the remains.
Clues directly from the skeleton may also indicate whether the remains are archaeological or modern. For example, tooth fillings can suggest that the individual was alive recently (Figure 16.8). In fact, filling material has changed over the decades, so the specific type of material used to fix a cavity can be matched with specific time periods. Gold was used in dental work in the past, but more recently composite (a mixture of plastic and fine glass) fillings have become more common.
How Many Individuals Are Present?
What Is MNI?
Another assessment that an anthropologist can perform is the calculation of the number of individuals in a mixed burial assemblage. Because not all burials consist of a single individual, it is important to burial assemblage be able to estimate the number of individuals in a forensic context. Quantification of the number of individuals in a burial assemblage can be done through the application of a number of methods, including the following: the Minimum Number of Individuals (MNI), the Most Likely Number of Individuals (MLNI), and the Lincoln Index (LI). The most commonly used method in biological anthropology, and the focus of this section, is determination of the MNI.
The MNI presents “the minimum estimate for the number of individuals that contributed to the sample” (Adams and Konigsberg 2008, 243). Many methods of calculating MNI were originally developed within the field of zooarchaeology for use on calculating the number of individuals in faunal or animal assemblages (Adams and Konigsberg 2008, 241). What MNI calculations provide is a lowest possible count for the total number of individuals contributing to a skeletal assemblage. Traditional methods of calculating MNI include separating a skeletal assemblage into categories according to the individual bone and the side the bone comes from and then taking the highest count per category and assigning that as the minimum number (Figure 16.9).
Why Calculate MNI?
In a forensic context, the determination of MNI is most applicable in cases of mass graves, commingled burials, and mass fatality incidents. The term commingled is applied to any burial assemblage in which individual skeletons are not separated into separate burials. As an example, the authors of this chapter have observed commingling of remains resulting from mass fatality wildfire events. Commingled remains may also be encountered in events such as a plane or vehicle crash. It is important to remember that in any forensic context, MNI should be referenced and an MNI of one should be substantiated by the fact that there was no repetition of elements associated with the case.
Constructing the Biological Profile
Who Is It?
“Who is it?” is one of the first questions that law enforcement officers ask when they are faced with a set of skeletal remains. To answer this question, forensic anthropologists construct a biological profile (White and Folkens 2005, 405). A biological profile is an individual’s identifying characteristics, or biological information, which include the following: biological sex, age at death, stature, population affinity, skeletal variation, and evidence of trauma and pathology.
Assessing Biological Sex
Assessment of biological sex is often one of the first things considered when establishing a biological profile because several other parts, such as age and stature estimations, rely on an assessment of biological sex to make the calculations more accurate.
Assessment of biological sex focuses on differences in both morphological (form or structure) and metric (measured) traits in individuals. When assessing morphological traits, the skull and the pelvis are the most commonly referenced areas of the skeleton. These differences are related to sexual dimorphism usually varying in the amount of robusticity seen between males and females. Robusticity deals with strength and size; it is frequently used as a term to describe a large size or thickness. In general, males will show a greater degree of robusticity than females. For example, the length and width of the mastoid process, a bony projection located behind the opening for the ear, is typically larger in males. The mastoid process is an attachment point for muscles of the neck, and this bony projection tends to be wider and longer in males. In general, cranial features tend to be more robust in males (Figure 16.10).
When considering the pelvis, the features associated with the ability to give birth help distinguish females from males. During puberty, estrogen causes a widening of the female pelvis to allow for the passage of a baby. Several studies have identified specific features or bony landmarks associated with the widening of the hips, and this section will discuss one such method. The Phenice Method (Phenice 1969) is traditionally the most common reference used to assess morphological characteristics associated with sex. The Phenice Method specifically looks at the presence or absence of (1) a ventral arc, (2) the presence or absence of a subpubic concavity, and (3) the width of the medial aspect of the ischiopubic ramus (Figure 16.11). When present, the ventral arc, a ridge of bone located on the ventral surface of the pubic bone, is indicative of female remains. Likewise the presence of a subpubic concavity and a narrow medial aspect of the ischiopubic ramus is associated with a female sex estimation. Assessments of these features, as well as those of the skull (when both the pelvis and skull are present), are combined for an overall estimation of sex.
Metric analyses are also used in the estimation of sex. Measurements taken from every region of the body can contribute to estimating sex through statistical approaches that assign a predictive value of sex. These approaches can include multiple measurements from several skeletal elements in what is called multivariate (multiple variables) statistics. Other approaches consider a single measurement, such as the diameter of the head of the femur, of a specific element in a univariate (single variable) analysis (Berg 2017, 152–156).
It is important to note that, although forensic anthropologists usually begin assessment of biological profile with biological sex, there is one major instance in which this is not appropriate. The case of two individuals found in California, on July 8, 1979, is one example that demonstrates the effect age has on the estimation of sex. The identities of the two individuals were unknown; therefore, law enforcement sent them to a lab for identification. A skeletal analysis determined that the remains represented one adolescent male and one adolescent female, both younger than 18 years of age. This information did not match with any known missing children at the time.
In 2015, the cold case was reanalyzed, and DNA samples were extracted. The results indicated that the remains were actually those of two girls who went missing in 1978. The girls were 15 years old and 14 years old at the time of death. It is clear that the 1979 results were incorrect, but this mistake also provides the opportunity to discuss the limitations of assessing sex from a subadult skeleton.
Assessing sex from the human skeleton is based on biological and genetic traits associated with females and males. These traits are linked to differences in sexual dimorphism and reproductive characteristics between females and males. The link to reproductive characteristics means that most indicators of biological sex do not fully manifest in prepubescent individuals, making estimations of sex unreliable in younger individuals (SWGANTH 2010b). This was the case in the example of the 14-year-old girl. When examined in 1979, her remains were misidentified as male because she had not yet fully developed female pelvic traits.
Sex vs. Gender
Biological sex is a different concept than gender. While biological anthropologists can estimate sex from the skeleton, estimating an individual’s gender would require a greater context because gender is defined culturally rather than biologically. Take, for example, an individual who identifies as transgender. This individual has a gender identity that is different from their biological sex. The gender identity of any individual depends on factors related to self-identification, situation or context, and cultural factors. While in the U.S. we have historically thought of sex and gender as binary concepts (male or female), many cultures throughout the world recognize several possible gender identities. In this sense, gender is seen as a continuous or fluid variable rather than a fixed one.
Historically, forensic anthropologists have used a binary construct to categorize human skeletal remains as either male or female (with the accompanying categories of probable male, probable female, and indeterminate). In the case of transgender and gender nonconforming individuals, the binary approach to sex assessment may delay or hinder identification efforts (Buchanan 2014; Schall, Rogers, and Deschamps-Braly 2020; Tallman, Kincer, and Plemons 2021). As such, many forensic anthropologists have begun to address the inherent problems associated with a binary approach to sex identification and to explore ways of assessing social identity and self-identified gender using skeletal remains and forensic context.
For the duration of this section, the term transgender refers to individuals whose gender identity differs from the sex assigned at birth (Schall, Rogers, and Deschamps-Braly 2020:2). Transgender individuals transition from one gender binary to another, such as male-to-female (MTF) or female-to-male (FTM). While many of the gender-affirming procedures available to trans and gender-nonconforming individuals are focused on soft tissue modifications (e.g., breast augmentation, genital reconstruction, hormone therapies, etc.), there are a number of gender-affirmation surgeries that do leave a permanent record on the skeleton. Generally speaking, FTM transgender people are reported to undergo fewer surgical procedures than do MTF transgender people (Buchanan 2014). The discussion below focuses on Facial Feminization Surgery (FFS), which leaves a permanent record on the human skeleton that may be used to help make an identification.
FFS refers to a combination of procedures focused on sexually dimorphic features of the face, with the intent of transforming typically male facial features into more feminine forms. Facial Feminization Surgery procedures were developed by Dr. Douglas Ousterhout, a San Francisco based cranio-maxillofacial surgeon, in the mid-1980s (Schall, Rogers, and Deschamps-Braly 2020:2). FFS can include one or a combination of the following: hairline lowering, forehead reduction and contouring, brow lift, reduction rhinoplasty, cheek enhancement, lip lift, lip filling, chin contouring, jaw contouring, and/or tracheal shave (Buchanan 2014; Schall, Rogers, and Deschamps-Braly 2020:2). Of the procedures outlined previously, four are known to directly affect the facial skeleton: forehead contouring, rhinoplasty, chin contouring, and jaw contouring (Buchanan 2014; Schall, Rogers, and Deschamps-Braly 2020:2).
Because FFS procedures have been widely documented in the medical (and more recently the forensic anthropological) literature, there are a number of indicators that a forensic anthropologist can use to make more informed evaluations of gender, including evidence of bone remodeling in sexually dimorphic regions of the skull (e.g., forehead, chin, jawline), as well as the presence of plates, pins, or other surgical hardware that may be evidence of FFS (Buchanan 2014; Schall, Rogers, and Deschamps-Braly 2020; Tallman, Kincer, and Plemons 2021). Additionally, some forensic anthropologists suggest cautiously integrating contextual information from the scene, such as personal effects, material evidence, and recovery scene information, into their evaluation of an individual’s social identity (Beatrice and Soler 2016; Birkby, Fenton, and Anderson 2008; Soler and Beatrice 2018; Soler et al. 2019; Tallman, Kincer, and Plemons 2021; Winburn, Schoff, and Warren 2016). The ultimate goal of many skeletal analyses is to make a positive identification on a set of unidentified remains.
Assessment of Population Affinity
In an effort to combat the erroneous assumptions tied to the race concept, forensic anthropologists have attempted to reframe this component of the biological profile. The term race is no longer used in casework and teaching. Historically, the word ancestry is and was deemed a more appropriate way to describe an individual’s phenotype. However, in more recent years, forensic anthropologists have begun using the term population affinity, recognizing that we are basing our analysis on the similarities we see based on the reference samples we have available (Winburn and Algee-Hewitt 2021). An important note here is that it is possible to hinder identifications and harm individuals when tools like estimations of population affinity are misapplied, misinterpreted, or misused. For this reason, the field of forensic anthropology has ongoing conversations about the appropriateness of this analysis in the biological profile (Bethard and DiGangi 2020; Stull et al. 2021).
We use the term population affinity to refer to the variation seen among modern populations—variation that is both genetic and environmentally driven. The word affinity refers to similarities or relationships between individuals. As forensic anthropologists, we compare an unknown individual to multiple reference groups and look for the degree of similarity in observable traits with those groups. As noted previously, population affinity can aid law enforcement in their identification of missing persons or unknown skeletal remains.
Within the field of anthropology, the estimation of population affinity has a contentious history, and early attempts at classification were largely based on the erroneous assumption that an individual’s phenotype (outward appearance) was correlated with their innate intelligence and abilities (see Chapter 13 for a more in-depth discussion of the history of the race concept). The use of the term race is deeply embedded in the social context of the United States. In any other organism/living thing, groups divided according to the biological race concept would be defined as a separate subspecies. The major issue with applying the biological race concept to humans is that there are not enough differences between any two populations to separate on a genetic basis. In other words, biological races do not exist in human populations. However, the concept of race has been perpetuated and upheld by sociocultural constructs of race.
The conundrum for forensic anthropologists is the fact that while races do not exist on a biological level, we still socially recognize and categorize individuals based on their phenotype. Clearly, our phenotype is an important factor in not only how we are viewed by others but also how we identify ourselves. It is also a commonly reported variable. Often labeled as “race,” we are asked to report how we self-identify on school applications, government identification, surveys, census reports, and so forth. It follows then that when a person is reported missing, the information commonly collected by law enforcement and sometimes entered into a missing person’s database includes their age, biological sex, stature, and “race.” Therefore, the more information a forensic anthropologist can provide regarding the individual’s physical characteristics, the more he or she can help to narrow the search.
As an exercise, create a list of all of the women you know who are between the ages of 18 and 24 and approximately 5’ 4” to 5’ 9” tall. You probably have several dozen people on the list. Now, consider how many females you know who are between the ages of 18 and 24, are approximately 5’ 4” to 5’ 9” tall, and are Vietnamese. Your list is going to be significantly shorter. That’s how missing persons searches go as well. The more information you can provide regarding a decedent’s phenotype, the fewer possible matches law enforcement are left to investigate. This is why population affinity has historically been included as a part of the biological profile.
Traditionally, population affinity was accomplished through a visual inspection of morphological variants of the skull (morphoscopics). These methods focused on elements of the facial skeleton, including the nose, eyes, and cheek bones. However, in an effort to reduce subjectivity, nonmetric cranial traits are now assessed within a statistical framework to help anthropologists better interpret their distribution among living populations (Hefner and Linde 2018). Based on the observable traits, a macromorphoscopic analysis will allow the practitioner to create a statistical prediction of geographic origin. In essence, forensic anthropologists are using human variation in the estimation of geographic origin, by referencing documented frequencies of nonmetric skeletal indicators or macromorphoscopic traits.
Population affinity is also assessed through metric analyses. The computer program Fordisc is an anthropological tool used to estimate different components of the biological profile, including ancestry, sex, and stature. When using Fordisc, skeletal measurements are input into the computer software, and the program employs multivariate statistical classification methods, including discriminant function analysis, to generate a statistical prediction for the geographic origin of unknown remains based on the comparison of the unknown to the reference samples in the software program. Fordisc also calculates the likelihood of the prediction being correct, as well as how typical the metric data is for the assigned group.
Estimating Age-at-Death
Estimating age-at-death from the skeleton relies on the measurement of two basic physiological processes: (1) growth and development and (2) degeneration (or aging). From fetal development on, our bones and teeth grow and change at a predictable rate. This provides for relatively accurate age estimates. After our bones and teeth cease to grow and develop, they begin to undergo structural changes, or degeneration, associated with aging. This does not happen at such predictable rates and, therefore, results in less accurate or larger age-range estimations.
During growth and development stages, two primary methods used for estimations of age of subadults (those under the age of 18) are epiphyseal union and dental development. Epiphyseal union (or epiphyseal fusion) refers to the appearance and closure of the epiphyseal plates between the primary centers of growth in a bone and the subsequent centers of growth (see Figure 16.7). Prior to complete union, the cartilaginous area between the primary and secondary centers of growth is also referred to as the growth plates (Schaefer, Black, and Scheuer 2009). Different areas of the skeleton have documented differences in the appearance and closure of epiphyses, making this a reliable method for aging subadult remains (SWGANTH 2013).
As an example of its utility in the identification process, epiphyseal development was used to identify two subadult victims of a fatal fire in Flint, Michigan, in February 2010. The remains represented two young girls, ages three and four. Due to the intensity of the fire, the subadult victims were differentiated from each other through the appearance of the patella, the kneecap. The patella is a bone that develops within the tendon of the quadriceps muscle at the knee joint. The patella begins to form around three to four years of age (Cunningham, Scheuer, and Black 2016, 407–409). In the example above, radiographs of the knees showed the presence of a patella in the four-year-old girl and the absence of a clearly discernible patella in the three-year-old.
Dental development begins during fetal stages of growth and continues until the complete formation and eruption of the adult third molars (if present). The first set of teeth to appear are called deciduous or baby teeth. Individuals develop a total of 20 deciduous teeth, including incisors, canines, and molars. These are generally replaced by adult dentition as an individual grows (Figure 16.12). A total of 32 teeth are represented in the adult dental arcade, including incisors, canines, premolars, and molars. When dental development is used for age estimations, researchers use both tooth-formation patterns and eruption schedules as determining evidence. For example, the crown of the tooth forms first followed by the formation of the tooth root. During development, an individual can exhibit a partially formed crown or a complete crown with a partially formed root. The teeth generally begin the eruption process once the crown of the tooth is complete. The developmental stages of dentition are one of the most reliable and consistent aging methods for subadults (Langley, Gooding, and Tersigni-Tarrant 2017, 176–177).
Degenerative changes in the skeleton typically begin after 18 years of age, with more prominent changes developing after an individual reaches middle adulthood (commonly defined as after 35 years of age in osteology). These changes are most easily seen around joint surfaces of the pelvis, the cranial vault, and the ribs. In this chapter, we focus on the pubic symphysis surfaces of the pelvis and the sternal ends of the ribs, which show metamorphic changes from young adulthood to older adulthood. The pubic symphysis is a joint that unites the left and right halves of the pelvis. The surface of the pubic symphysis changes during adulthood, beginning as a surface with pronounced ridges (called billowing) and flattening with a more distinct rim to the pubic symphysis as an individual ages. As with all metamorphic age changes, older adults tend to develop lipping around the joint surfaces as well as a breakdown of the joint surfaces. The most commonly used method for aging adult skeletons from the pubic symphysis is the Suchey-Brooks method (Brooks and Suchey 1990; Katz and Suchey 1986). This method divides the changes seen with the pubic symphysis into six phases based on macroscopic age-related changes to the surface. Figure 16.13 provides a visual of the degenerative changes that typically occur on the pubic symphysis.
The sternal end of the ribs, the anterior end of the rib that connects via cartilage to the sternum, is also used in age estimations of adults. This method, first developed by M. Y. İşcan and colleagues, considers both the change in shape of the sternal end as well as the quality of the bone (İşcan, Loth, and Wright 1984; İşcan, Loth, and Wright 1985). The sternal end first develops a billowing appearance in young adulthood. The bone typically develops a wider and deeper cupped end as an individual ages. Older adults tend to exhibit bony extensions of the sternal end rim as attaching cartilage ossifies. Figure 16.14 provides a visual of the degenerative changes that typically occur in sternal rib ends.
Estimating Stature
Stature, or height, is one of the most prominently recorded components of the biological profile. Our height is recorded from infancy through adulthood. Doctor’s appointments, driver's license applications, and sports rosters all typically involve a measure of stature for an individual. As such, it is also a component of the biological profile nearly every individual will have on record. Bioarchaeologists and forensic anthropologists use stature estimation methods to provide a range within which an individual’s biological height would fall. Biological height is a person’s true anatomical height. However, the range created through these estimations is often compared to reported stature, which is typically self-reported and based on an approximation of an individual’s true height (Ousley 1995).
In June 2015, two men were shot and killed in Granite Bay, California, in a double homicide. Investigators were able to locate surveillance camera footage from a gas station where the two victims were spotted in a car with another individual believed to be the perpetrator in the case. The suspect, sitting behind the victims in the car, hung his right arm out of the window as the car drove away. The search for the perpetrator was eventually narrowed down to two suspects. One suspect was 5’ 8” while the other suspect was 6’ 4”, representing almost a foot difference in height reported stature between the two. Forensic anthropologists were given the dimensions of the car (for proportionality of the arm) and were asked to calculate the stature of the suspect in the car from measurements of the suspect’s forearm hanging from the window. Approximate lengths of the bones of the forearm were established from the video footage and used to create a predicted stature range. Stature estimations from skeletal remains typically look at the correlation between the measurements of any individual bone and the overall measurement of body height. In the case above, the length of the right forearm pointed to the taller of the two suspects who was subsequently arrested for the homicide.
Certain bones, such as the long bones of the leg, contribute more to our overall height than others and can be used with mathematical equations known as regression equations. Regression methods examine the relationship between variables such as height and bone length and use the correlation between the variables to create a prediction interval (or range) for estimated stature. This method for calculating stature is the most commonly used method (SWGANTH 2012). Figure 16.15 shows the measurement of the bicondylar length of the femur for stature estimations.
Identification Using Individualizing Characteristics
One of the most frequently requested analyses within the forensic anthropology laboratory is assistance with the identification of unidentified remains. While all components of a biological profile, as discussed above, can assist law enforcement officers and medical examiners to narrow down the list of potential identifications, a biological profile will not lead to a positive identification. The term positive identification refers to a scientifically validated method of identifying previously unidentified remains. Presumptive identifications, however, are not scientifically validated; rather, they are based on circumstances or scene context. For example, if a decedent is found in a locked home with no evidence of forced entry but the body is no longer visually identifiable, it may be presumed that the remains belong to the homeowner. Hence, a presumptive identification.
The medicolegal system ultimately requires that a positive identification be made in such circumstances, and a presumptive identification is often a good way to narrow down the pool of possibilities. Biological profile information also assists with making a presumptive identification based on an individual’s phenotype in life (e.g., what they looked like). As an example, a forensic anthropologist may establish the following components of a biological profile: white male, between the ages of 35 and 50, approximately 5’ 7” to 5’ 11.” While this seems like a rather specific description of an individual, you can imagine that this description fits dozens, if not hundreds, of people in an urban area. Therefore, law enforcement can use the biological profile information to narrow their pool of possible identifications to include only white males who fit the age and height outlined above. Once a possible match is found, the decedent can be identified using a method of positive identification.
Positive identifications are based on what we refer to as individualizing traits or characteristics, which are traits that are unique at the individual level. For example, brown hair is not an individualizing trait as brown is the most common hair color in the U.S. But, a specific pattern of dental restorations or surgical implants can be individualizing, because it is unlikely that you will have an exact match on either of these traits when comparing two individuals.
A number of positive methods are available to forensic anthropologists, and for the remainder of this section we will discuss the following methods: comparative medical and dental radiography and identification of surgical implants.
Comparative medical and dental radiography is used to find consistency of traits when comparing antemortem records (medical and dental records taken during life) with images taken postmortem (after death). Comparative medical radiography focuses primarily on features associated with the skeletal system, including trabecular pattern (internal structure of bone that is honeycomb in appearance), bone shape or cortical density (compact outer layer of bone), and evidence of past trauma, skeletal pathology, or skeletal anomalies. Other individualizing traits include the shape of various bones or their features, such as the frontal sinuses (Figure 16.16).
Comparative dental radiography focuses on the number, shape, location, and orientation of dentition and dental restorations in antemortem and postmortem images. While there is not a minimum number of matching traits that need to be identified for an identification to be made, the antemortem and postmortem records should have enough skeletal or dental consistencies to conclude that the records did in fact come from the same individual (SWGANTH 2010a). Consideration should also be given to population-level frequencies of specific skeletal and dental traits. If a trait is particularly common within a given population, it may not be a good trait to utilize for positive identification.
Surgical implants or devices can also be used for identification purposes (Figure 16.17). These implements are sometimes recovered with human remains. One of the ways forensic anthropologists can use surgical implants to assist in decedent identification is by providing a thorough analysis of the implant and noting any identifying information such as serial numbers, manufacturer symbols, and so forth. This information can then sometimes be tracked directly to the manufacturer or the place of surgical intervention, which may be used to identify unknown remains (SWGANTH 2010a).
Special Topic: Trans Doe Task Force
The Trans Doe Task Force (TDTF) is a Trans-led nonprofit organization that investigates cases involving LGBTQ+ missing and murdered persons. The organization specifically focuses on transgender and gender-variant cases, providing connections between law enforcement agencies, medical examiner offices, forensic anthropologists, and forensic genetic genealogists to increase the chances of identification. Additionally, the TDTF curates a data repository of missing, murdered, and unclaimed LGBTQ+ individuals, and they continuously try innovative approaches to identify these individuals, whose lived gender identity may not match their biological sex.
For more information visit transdoetaskforce.org
Trauma Analysis
Types of Trauma
Within the field of anthropology, trauma is defined as an injury to living tissue caused by an extrinsic force or mechanism (Lovell 1997:139). Forensic anthropologists can assist a forensic pathologist by providing an interpretation of the course of events that led to skeletal trauma. Typically, traumatic injury to bone is classified into one of four categories, defined by the trauma mechanism. A trauma mechanism refers to the force that produced the skeletal modification and can be classified as (1) sharp force, (2) blunt force, (3) projectile, or (4) thermal (burning). Each type of trauma, and the characteristic pattern(s) associated with that particular categorization, will be discussed below.
First, let’s consider sharp-force trauma, which is caused by a tool that is edged, pointed, or beveled—for example, a knife, saw, or machete (SWGANTH 2011). The patterns of injury resulting from sharp-force trauma include linear incisions created by a sharp, straight edge; punctures; and chop marks (Figure 16.18; SWGANTH 2011). When observed under a microscope, an anthropologist can often determine what kind of tool created the bone trauma. For example, a power saw cut will be discernible from a manual saw cut.
Second, blunt-force trauma is defined as “a relatively low-velocity impact over a relatively large surface area” (Galloway 1999, 5). Blunt-force injuries can result from impacts from clubs, sticks, fists, and so forth. Blunt-force impacts typically leave an injury at the point of impact but can also lead to bending and deformation in other regions of the bone. Depressions, fractures, and deformation at and around the site of impact are all characteristics of blunt-force trauma (Figure 16.19). As with sharp-force trauma, an anthropologist attempts to interpret blunt-force injuries, providing information pertaining to the type of tool used, the direction of impact, the sequence of impacts, if more than one, and the amount of force applied.
Third, projectile trauma refers to high-velocity trauma, typically affecting a small surface area (Galloway 1999, 6). Projectile trauma results from fast-moving objects such as bullets or shrapnel. It is typically characterized by penetrating defects or embedded materials (Figure 16.20). When interpreting injuries resulting from projectile trauma, an anthropologist can often offer information pertaining to the type of weapon used (e.g., rifle vs. handgun), relative size of the bullet (but not the caliber of the bullet), the direction the projectile was traveling, and the sequence of injuries if there are multiple present.
Finally, thermal trauma is a bone alteration that results from bone exposure to extreme heat. Thermal trauma can result in cases of house or car fires, intentional disposal of a body in cases of homicidal violence, plane crashes, and so on. Thermal trauma is most often characterized by color changes to bone, ranging from yellow to black (charred) or white (calcined). Other bone alterations characteristic of thermal trauma include delamination (flaking or layering due to bone failure), shrinkage, fractures, and heat-specific burn patterning. When interpreting injuries resulting from thermal damage, an anthropologist can differentiate between thermal fractures and fractures that occurred before heat exposure, thereby contributing to the interpretation of burn patterning (e.g., was the individual bound or in a flexed position prior to the fire?).
While there are characteristic patterns associated with the four categories of bone trauma, it is also important to note that these bone alterations do not always occur independently of different trauma types. An individual’s skeleton may present with multiple different types of trauma, such as a projectile wound and thermal trauma. Therefore, it is important that the anthropologist recognize the different types of trauma and interpret them appropriately.
Timing of Injury
Another important component of any anthropological trauma analysis is the determination of the timing of injury (e.g., when did the injury occur). Timing of injury is traditionally split into one of three categories: antemortem (before death), perimortem (at or around the time of death), and postmortem (after death). This classification system differs slightly from the classification system used by the pathologist because it specifically references the qualities of bone tissue and bone response to external forces. Therefore, the perimortem interval (at or around the time of death) means that the bone is still fresh and has what is referred to as a green bone response, which can extend past death by several weeks or even months. For example, in cold or freezing temperatures a body can be preserved for extended periods of time, increasing the perimortem interval, while in desert climates decomposition is accelerated, thereby significantly decreasing the postmortem interval (Galloway 1999, 12). Antemortem injuries (occurring well before death and not related to the death incident) are typically characterized by some level of healing, in the form of a fracture callus or unification of fracture margins. Finally, postmortem injuries (occurring after death, while bone is no longer fresh) are characterized by jagged fracture margins, resulting from a loss of moisture content during the decomposition process (Galloway 1999, 16). In general, all bone traumas should be classified according to the timing of injury, if possible. This information will help the medical examiner or pathologist better understand the circumstances surrounding the decedent’s death, as well as events occurring during life and after the final disposition of the body.
The Role of the Forensic Anthropologist in Trauma Analysis
Within the medicolegal system, forensic anthropologists are often called upon by the medical examiner, forensic pathologist, or coroner to assist with an interpretation of trauma. The forensic anthropologist’s main focus in any trauma analysis is the underlying skeletal system—as well as, sometimes, cartilage. Analysis and interpretation of soft tissue injuries fall within the purview of the medical examiner or pathologist. It is also important to note that the main role of the forensic anthropologist is to provide information pertaining to skeletal injury to assist the medical examiner/pathologist in their final interpretation of injury. Forensic anthropologists do not hypothesize as to the cause of death of an individual. Instead, a forensic anthropologist’s report should include a description of the injury (e.g., trauma mechanism, number of injuries, location, timing of injury); documentation of the injury, which may be utilized in court testimony (e.g., photographs, radiographs, measurements); and, if applicable, a statement as to the condition of the body and state of decomposition, which may be useful for understanding the depositional context (e.g., how long has the body been exposed to the elements; was it moved or in its original location; are any of the alterations to bone due to environmental or faunal exposure instead of intentional human modification).
Taphonomy
What Happened to the Remains After Death?
The majority of the skeletal analysis process revolves around the identity of the deceased individual. However, there is one last, very important question that forensic anthropologists should ask: What happened to the remains after death? Generally speaking, processes that alter the bone after death are referred to as taphonomic changes (refer to Chapter 7 for a discussion regarding taphonomy and the fossil record).
The term taphonomy was originally used to refer to the processes through which organic remains mineralize, also known as fossilization. Within the context of biological anthropology, the term taphonomy is better defined as the study of what happens to human remains after death (Komar and Buikstra 2008). Initial factors affecting a body after death include processes such as decomposition and scavenging by animals. However, taphonomic processes encompass much more than the initial period after death. For example, plant root growth can leach minerals from bone, leaving a distinctive mark. Sunlight can bleach human remains, leaving exposed areas whiter than those that remained buried. Water can wear the surface of the bone until it becomes smooth.
Some taphonomic processes can help a forensic anthropologist estimate the relative amount of time that human remains have been exposed to the elements. For example, root growth through a bone would certainly indicate a body was buried for more than a few days. Forensic anthropologists must be very careful when attempting to estimate time since death based on taphonomic processes because environmental conditions can greatly influence the rate at which taphonomic processes progress. For example, in cold environments, tissue may decay slower than in warm, moist environments.
Forensic anthropologists must contend with taphonomic processes that affect the preservation of bones. For example, high acidity in the soil can break down human bone to the point of crumbling. In addition, when noting trauma, they must be very careful not to confuse postmortem (after death) bone damage with trauma.
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Taphonomic Process |
Definition |
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Rodent Gnawing
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When rodents, such as rats and mice, chew on bone, they leave sets of parallel grooves. The shallow grooves are etched by the rodent’s incisors. |
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Carnivore Damage
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Carnivores may leave destructive dental marks on bone. The tooth marks may be visible as pit marks or punctures from the canines, as well as extensive gnawing or chewing of the ends of the bones to retrieve marrow. |
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Burned Bone
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Fire causes observable damage to bone. Temperature and the amount of time bone is heated affect the appearance of the bone. Very high temperatures can crack bone and result in white coloration. Color gradients are visible in between high and lower temperatures, with lower temperatures resulting in black coloration from charring. Cracking can also reveal information about the directionality of the burn. |
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Root Etching
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Plant roots can etch the outer surface of bone, leaving grooves where the roots attached as they leached nutrients. During this process, the plant’s roots secrete acid that breaks down the surface of the bone.
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Weathering
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Many different environmental conditions affect bone. River transport can smooth the surface of the bone due to water abrasion. Sunlight can bleach the exposed surface of bone. Dry and wet environments or the mixture of both types of environments can cause cracking and exfoliation of the surface. Burial in different types of soil can cause discoloration, and exposure can cause degreasing. |
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Cut Marks
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Humans may alter bone by cutting, scraping, or sawing it directly or in the process of removing tissue. The groove pattern—that is, the depth and width of the cuts—can help identify the tool used in the cutting process. |
Dig Deeper: Modern Forensic Technologies
In recent years, the forensics community has greatly benefited from the introduction of new technologies, helping strengthen the precision and speed of discoveries and advancements in the field. With recent developments in forensic anthropology, such as 3D scanning technologies, virtual reconstruction, and AI-assisted DNA analysis being integrated into traditional methods, there have been notable changes in how experts investigate human remains.
Artificial intelligence
In recent years, Artificial intelligence (AI) has shown itself to be a valuable tool within forensic anthropology. Aiding forensic experts and toxicologists with complex tasks, the limitations of traditional autopsies can be addressed with the help of AI. By automating and enhancing key investigative processes such as searching for microscopic changes in the human body to determine the cause of death or a person’s life conditions, AI has the potential to enhance the efficiency of forensic processes significantly. It facilitates the detection of microscopic bodily changes to determine the cause of death or living conditions, compares evidence against databases for weapon identification and blood spatter analysis, and reduces manual workload. AI also enables the electronic storage of biometric data–such as facial features, retinal patterns, and fingerprints–for more accurate identity verification. Additionally, AI-powered microscopy enhances the detection of biological traces on complex surfaces, while blood biomarker analysis allows for more precise estimations of time of death (Wankhade et al., 2022).
While AI holds great promise for the future of forensic medicine, a significant challenge remains: sourcing high-quality data to train the algorithms effectively. One of the more recent AI technologies making waves in the forensic anthropology sector is a new automated AI algorithm called the Convolutional Neural Network (CNN). As described by researchers in Switzerland’s national medical journal Healthcare, CNN is a Deep Learning algorithm that allows for the detection of microscopic skull damage from CT scans or soft-tissue predictions of a face based on the skull information provided (Thurzo et al., 2021). While there are many advantages to using the CNN, the algorithm can be subject to biases in the same way human forensic experts can, as its assessment and pattern recognition of skulls and skeletons depend on the source data initially used for its AI training (2021).
3D Modeling
Identifying complex trauma to bones–such as distinguishing heat fractures following blunt force trauma–remains a significant challenge in forensic anthropology. This is particularly true for irregular skeletal structures like the pelvis, where overlapping trauma types can be difficult to differentiate, leading to these bones often being understudied. A 2024 study done by researchers from the University of Alberta in collaboration with the Michigan State Police explores the use of 3D laser scans and modelling technology to provide a highly detailed analysis of irregular bones with trauma. The study aimed to better distinguish peri-mortem trauma (trauma occurring around the time of death) from post-mortem heat alterations and improve the forensic analysis accuracy of such cases (Friedlander et al., 2024). The use of 3D laser scans and modelling technology provides very clear, detailed, and colored scans of bones, showing distinctions between the characteristics of the fractures. Blunt force and sharp force trauma produce a colour gradient on the 3D model that is more gradual and irregular, while heat fractures are more neat and characterized by little colour variation on the 3D models (2024). Other conclusions were also drawn from the study, such as the differences in trauma on fresh bones and bones that have been exposed to the elements for longer. An example of this is the interstitial fluid and collagen fibrils in fresh bones absorbing force, causing more long and jagged fracture lines, as opposed to a brittle fracture that older bones may exhibit (2024).
Overall, the integration of 3D modeling technology offers a reproducible and highly detailed approach for analyzing trauma in anatomically complex and historically understudied skeletal regions. The practicality of this advancement is further emphasized by the researchers, who note that “in many instances, scanned 3D models can be 3D printed for handheld representation of the model without damaging or overhandling the remains” (2024, p. 2). By enhancing the ability to differentiate between various types of trauma and allowing for more convenient and risk-averse methods of research, this technology significantly improves the accuracy and reliability of forensic interpretations.
Ethics and Human Rights
Working with human remains requires a great deal of consideration and respect for the dead. Forensic anthropologists have to think about the ethics of our use of human remains for scientific purposes. How do we conduct casework in the most respectable manner possible? While there are a wide range of ethical considerations to consider when contemplating a career in forensic anthropology, this chapter will focus on two major categories: working with human remains and acting as an expert within the medicolegal system.
Working with Human Remains
Forensic anthropologists work with human remains in a number of contexts, including casework, excavation, research, and teaching. When working with human remains, it is always important to use proper handling techniques. To prevent damage to skeletal remains, bones should be handled over padded surfaces. Skulls should never be picked up by placing fingers in the eye orbits, foramen magnum (hole at the base of the skull for entry of the spinal cord), or through the zygomatic arches (cheekbones). Human remains, whether related to casework, fieldwork, donated skeletal collections, or research, were once living human beings. It is important to always bear in mind that work with remains should be ingrained with respect for the individual and their relatives. In addition to fieldwork, casework, and teaching, anthropologists are often invited to work with remains that come from a bioarchaeological context or from a human rights violation. While this discussion of ethics is not comprehensive, two case examples will be provided below in which an anthropologist must consider the ethical standards outlined above.
Modern Human Rights Violations
Forensic anthropologists may also be called to participate in criminal investigations involving human rights violations. Anthropological investigations may include assistance with identifications, determination of the number of victims, and trauma analyses. In this role, forensic anthropologists play an integral part in promoting human rights, preventing future human rights violations, and providing the evidence necessary to prosecute those responsible for past events. A few ethical considerations for the forensic anthropologist involved in human rights violations include the use of appropriate standards of identification, presenting reliable and unbiased testimony, and maintaining preservation of evidence. For a more comprehensive history of forensic anthropological contributions to human rights violations investigations, see Ubelaker 2018.
Acting as an Expert in the Medicolegal System
In addition to the ethical considerations involved in working with human skeletal remains, forensic anthropologists must abide by ethical standards when they act as experts within the medicolegal system. The role of the forensic anthropologist within the medicolegal system is primarily to provide information to the medical examiner or coroner that will aid in the identification process or determination of cause and manner of death. Forensic anthropologists also may be called to testify in a court of law. In this capacity, forensic anthropologists should always abide by a series of ethical guidelines that pertain to their interpretation, presentation, and preservation of evidence used in criminal investigations. First and foremost, practitioners should never misrepresent their training or education. When appropriate, outside opinions and assistance in casework should be requested (e.g., consulting a radiologist for radiological examinations or odontologist for dental exams). The best interest of the decedent should always take precedence. All casework should be conducted in an unbiased way, and financial compensation should never be accepted as it can act as an incentive to take a biased stance regarding casework. All anthropological findings should be kept confidential, and release of information is best done by the medical examiner or coroner. Finally, while upholding personal ethical standards, forensic anthropologists are also expected to report any perceived ethical violations committed by their peers.
Ethical standards for the field of forensic anthropology are outlined by the Organization of Scientific Area Committees (OSAC) for Forensic Science, administered by the National Institute of Standards and Technology (NIST). OSAC and NIST recently began an initiative to develop standards that would strengthen the practice of forensic science both in the United States and internationally. OSAC’s main objective is to “strengthen the nation’s use of forensic science by facilitating the development of technically sound forensic science standards and by promoting the adoption of those standards by the forensic science community” (NIST n.d.). Additionally, OSAC promotes the establishment of best practices and other guidelines to ensure that forensic science findings and their presentation are reliable and reproducible (NIST 2023).
Special Topic: Native American Graves Protection and Repatriation Act (NAGPRA)
There is a long history in the United States of systematic disenfranchisement of Native American people, including lack of respect for tribal sovereignty. This includes the egregious treatment of Native American human remains. Over several centuries, thousands of Native American remains were removed from tribal lands and held at institutions in the United States, such as museums and universities.
In 1990, a landmark human rights federal law, the Native American Graves Protection and Repatriation Act (NAGPRA), spurred change in the professional standards and practice of biological anthropology and archaeology. NAGPRA established a legal avenue to provide protection for and repatriation of Native American remains, cultural items, and sacred objects removed from Federal or tribal lands to Native American lineal descendants, Indian tribes, and Native Hawaiian organizations. Human remains and associated artifacts, curated in museum collections and federally funded institutions, are subject to three primary provisions outlined by the NAGPRA statute: (1) protection for Native graves on federal and private land; (2) recognition of tribal authority on such lands; and (3) the requirement that all Native skeletal remains and associated artifacts be inventoried and culturally affiliated groups be consulted concerning decisions related to ownership and final disposition (Rose, Green, and Green 1996). NAGPRA legislation was enacted to ensure ethical consideration and treatment of Native remains and to improve dialogue between scientists and Native groups.
- For more information about NAGPRA, visit the Bureau of Reclamation NAGPRA website
- To read the text of the law, visit the US Congress NAGPRA law website.
- For further discussion of NAGPRA history, please see TRACES: An Open Invitation to Archaeology open textbook website
Becoming a Forensic Anthropologist
What does it take to be a forensic anthropologist? Forensic anthropologists are first and foremost anthropologists. While many forensic anthropologists have an undergraduate degree in anthropology, they may also major in biology, criminal justice, pre-law, pre-med, and many other related fields. Practicing forensic anthropologists typically have an advanced degree, either a Master’s or Doctoral degree in Anthropology. Additional training and experience in archaeology, the medico-legal system, rules of evidence, and expert witness testimony are also common. Practicing forensic anthropologists are also encouraged to be board-certified through the American Board of Forensic Anthropology (ABFA). Learn more about the field and educational opportunities on the ABFA website: https://www.theabfa.org/coursework.
Summary
As a subfield of biological anthropology, forensic anthropology encompasses a wide range of methods used to better understand human remains, whether from the present or the past. Through skeletal analysis, forensic anthropologists approach the study of the deceased from multiple perspectives. For instance, they may begin by identifying whether bones are human or animal, determining whether they are modern or archaeological, and assessing whether the remains were buried alone or as part of a larger assemblage. These initial steps provide a foundation for interpreting what the remains represent.
Once a clearer understanding of the remains is established, forensic anthropologists can construct a biological profile of the individual. This process involves estimating biological sex, population affinity, age at death, and stature, as well as examining unique or individualizing features. Together, these elements allow anthropologists to build a more complete picture of the deceased.
Another central responsibility of forensic anthropologists is investigating how the individual died. Trauma analysis plays a key role in this process: Was the person affected by sharp force, blunt force, projectile injuries, or thermal damage? Determining the timing of injuries (whether they occurred before, at, or after death) along with analyzing what happened to the remains afterward, helps anthropologists understand both the cause and context of death. Taphonomic changes provide additional insight into the circumstances surrounding an individual’s final moments.
Working with human remains requires careful consideration and profound respect for the deceased. For this reason, strict methods and ethical guidelines are integral to the profession. Proper handling techniques ensure that human remains are treated with dignity, while ethical standards guide anthropologists in their dual role within both medical and legal systems. Because their expertise can influence the interpretation and presentation of evidence in criminal investigations, forensic anthropologists must adhere to ethical principles. These standards are outlined by the Organization of Scientific Area Committees (OSAC) for Forensic Science, administered by the National Institute of Standards and Technology (NIST).
Review Questions
- What is forensic anthropology? What are the seven primary steps involved in a skeletal analysis?
- What are the major components of a biological profile? Why are forensic anthropologists often-tasked with creating biological profiles for unknown individuals?
- What are the four major types of skeletal trauma?
- What is taphonomy, and why is an understanding of taphonomy often critical in forensic anthropology analyses?
- What are some of the ethical considerations faced by forensic anthropologists?
For Further Exploration
The American Board of Forensic Anthropology (ABFA)
The American Academy of Forensic Sciences (AAFS)
The Organization of Scientific Area Committees for Forensic Science (OSAC)
References
Adams, Bradley J., and Lyle W. Konigsberg, eds. 2008. Recovery, Analysis, and Identification of Commingled Remains. Totowa, NJ: Humana Press.
Beatrice, Jared S., and Angela Soler. 2016. “Skeletal Indicators of Stress: A Component of the Biocultural Profile of Undocumented Migrants in Southern Arizona.” Journal of Forensic Sciences 61 (5): 1164–1172.
Berg, Gregory E. 2017. “Sex Estimation of Unknown Human Skeletal Remains.” In Forensic Anthropology: A Comprehensive Introduction, Second Edition, edited by Natalie R. Langley and MariaTeresa A. Tersigni-Tarrant, 143–159. Boca Raton, FL: CRC Press.
Bethard, Jonathan D., and Elizabeth A. DiGangi. 2020. “Letter to the Editor—Moving Beyond a Lost Cause: Forensic Anthropology and Ancestry Estimates in the United States.” Journal of Forensic Sciences 65 (5): 1791–1792.
Birkby, Walter H., Todd W. Fenton, and Bruce E. Anderson. 2008. “Identifying Southwest Hispanics Using Nonmetric Traits and the Cultural Profile.” Journal of Forensic Sciences 53 (1): 29–33.
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Keith Chan, Ph.D., Grossmont-Cuyamaca Community College District and MiraCosta College
This chapter is a revision from "Chapter 12: Modern Homo sapiens” by Keith Chan. In Explorations: An Open Invitation to Biological Anthropology, first edition, edited by Beth Shook, Katie Nelson, Kelsie Aguilera, and Lara Braff, which is licensed under CC BY-NC 4.0.
Learning Objectives
- Identify the skeletal and behavioral traits that represent modern Homo sapiens.
- Critically evaluate different types of evidence for the origin of our species in Africa and our expansion around the world.
- Understand how the human lifestyle changed when people transitioned from foraging to agriculture.
- Hypothesize how human evolutionary trends may continue into the future.
The walls of a pink limestone cave in the hillside of Jebel Irhoud jutted out of the otherwise barren landscape of the Moroccan desert (Figure 13.1). Miners had excavated the cave in the 1960s, revealing some fossils. In 2007, a re-excavation of the site became a momentous occasion for science. A fossil cranium unearthed by a team of researchers was barely visible to the untrained eye. Just the fossil’s robust brows were peering out of the rock. This research team from the Max Planck Institute for Evolutionary Anthropology was the latest to explore the ancient human presence in this part of North Africa after a find by miners in 1960. Excavating near the first discovery, the researchers wanted to learn more about how Homo sapiens lived far from East Africa, where we thought our species originated.
The scientists were surprised when they analyzed the cranium, named Irhoud 10, and other fossils. Statistical comparisons with other human crania concluded that the Irhoud face shapes were typical of recent modern humans while the braincases matched ancient modern humans. Based on the findings of other scientists, the team expected these modern Homo sapiens fossils to be around 200,000 years old. Instead, dating revealed that the cranium had been buried for around 315,000 years.
Together, the modern-looking facial dimensions and the older date reshaped the interpretation of our species: modern Homo sapiens. Some key evolutionary changes from the archaic Homo sapiens (described in Chapter 11) to our species today happened 100,000 years earlier than we had thought and across the vast African continent rather than concentrated in its eastern region.
This revelation in the study of modern Homo sapiens is just one of the latest in this continually advancing area of biological anthropology. Researchers today are still discovering amazing fossils and ingenious ways to collect data and test hypotheses about our past. Through the collective work of many scientists, we are building an overall theory of modern human origins.
Defining Modernity
What defines modern Homo sapiens when compared to archaic Homo sapiens? Modern humans, like you and me, have a set of derived traits that are not seen in archaic humans or any other hominin. As with other transitions in hominin evolution, such as increasing brain size and bipedal ability, modern traits do not appear fully formed or all at once. In other words, the first modern Homo sapiens was not just born one day from archaic parents. The traits common to modern Homo sapiens appeared in a mosaic manner: gradually and out of sync with one another. There are two areas to consider when tracking the complex evolution of modern human traits. One is the physical change in the skeleton. The other is behavior inferred from the size and shape of the cranium and material culture evidence.
Skeletal Traits
The skeleton of modern Homo sapiens is less robust than that of archaic Homo sapiens. In other words, the modern skeleton is gracile, meaning that the structures are thinner and smoother. Differences related to gracility in the cranium are seen in the braincase, the face, and the mandible. There are also broad differences in the rest of the skeleton.
Cranial Traits
Several elements of the braincase differ between modern and archaic Homo sapiens. Overall, the shape is much rounder, or more globular, on a modern skull (Lieberman, McBratney, and Krovitz 2002; Neubauer, Hublin, and Gunz 2018; Pearson 2008; Figure 13.2). You can feel the globularity of your own modern human skull. Feel the height of your forehead with the palm of your hand. Viewed from the side, the tall vertical forehead of a modern Homo sapiens stands out when compared to the sloping archaic version. This is because the frontal lobe of the modern human brain is larger than the one in archaic humans, and the skull has to accommodate the expansion. The vertical forehead reduces a trait that is common to all other hominins: the brow ridge or supraorbital torus. The parietal lobes of the brain and the matching parietal bones on either side of the skull both bulge outward more in modern humans. At the back of the skull, the archaic occipital bun is no longer present. Instead, the occipital region of the modern human cranium has a derived tall and smooth curve, again reflecting the globular brain inside.
The trend of shrinking face size across hominins reaches its extreme with our species as well. The facial bones of a modern Homo sapiens are extremely gracile compared to all other hominins (Lieberman, McBratney, and Krovitz 2002). Continuing a trend in hominin evolution, technological innovations kept reducing the importance of teeth in reproductive success (Lucas 2007). As natural selection favored smaller and smaller teeth, the surrounding bone holding these teeth also shrank.
Related to smaller teeth, the mandible is also gracile in modern humans when compared to archaic humans and other hominins. Interestingly, our mandibles have pulled back so far from the prognathism of earlier hominins that we gained an extra structure at the most anterior point, called the mental eminence. You know this structure as the chin. At the skeletal level, it resembles an upside-down “T” at the centerline of the mandible (Pearson 2008). Looking back at archaic humans, you will see that they all lack a chin. Instead, their mandibles curve straight back without a forward point. What is the chin for and how did it develop? Flora Gröning and colleagues (2011) found evidence of the chin’s importance by simulating physical forces on computer models of different mandible shapes. Their results showed that the chin acts as structural support to withstand strain on the otherwise gracile mandible.
Postcranial Gracility
The rest of the modern human skeleton is also more gracile than its archaic counterpart. The differences are clear when comparing a modern Homo sapiens with a cold-adapted Neanderthal (Sawyer and Maley 2005), but the trends are still present when comparing modern and archaic humans within Africa (Pearson 2000). Overall, a modern Homo sapiens postcranial skeleton has thinner cortical bone, smoother features, and more slender shapes when compared to archaic Homo sapiens (Figure 13.3). Comparing whole skeletons, modern humans have longer limb proportions relative to the length and width of the torso, giving us lankier outlines.
Why is our skeleton so gracile compared to those of other hominins? Natural selection can drive the gracilization of skeletons in several ways (Lieberman 2015). A slender frame is believed to be adapted for the efficient long-distance running ability that started with Homo erectus. Furthermore, it is argued that slenderness is a genetic adaptation for cooling an active body in hotter climates, which aligns with the ample evidence that Africa was the home continent of our species.
Behavioral Modernity
Aside from physical differences in the skeleton, researchers have also uncovered evidence of behavioral changes associated with increased cultural complexity from archaic to modern humans. How did cultural complexity develop? Two investigations into this question are archaeology and the analysis of reconstructed brains.
Archaeology tells us much about the behavioral complexity of past humans by interpreting the significance of material culture. In terms of advanced culture, items created with an artistic flair, or as decoration, speak of abstract thought processes (Figure 13.4). The demonstration of difficult artistic techniques and technological complexity hints at social learning and cooperation as well. According to paleoanthropologist John Shea (2011), one way to track the complexity of past behavior through artifacts is by measuring the variety of tools found together. The more types of tools constructed with different techniques and for different purposes, the more modern the behavior. Researchers are still working on an archaeological way to measure cultural complexity that is useful across time and place.
The interpretation of brain anatomy is another promising approach to studying the evolution of human behavior. When looking at investigations on this topic in modern Homo sapiens brains, researchers found a weak association between brain size and test-measured intelligence (Pietschnig et al. 2015). Additionally, they found no association between intelligence and biological sex. These findings mean that there are more significant factors that affect tested intelligence than just brain size. Since the sheer size of the brain is not useful for weighing intelligence within a species, paleoanthropologists are instead investigating the differences in certain brain structures. The differences in organization between modern Homo sapiens brains and archaic Homo sapiens brains may reflect different cognitive priorities that account for modern human culture. As with the archaeological approach, new discoveries will refine what we know about the human brain and apply that knowledge to studying the distant past.
Taken together, the cognitive abilities in modern humans may have translated into an adept use of tools to enhance survival. Researchers Patrick Roberts and Brian A. Stewart (2018) call this concept the generalist-specialist niche: our species is an expert at living in a wide array of environments, with populations culturally specializing in their own particular surroundings. The next section tracks how far around the world these skeletal and behavioral traits have taken us.
First Africa, Then the World
What enabled modern Homo sapiens to expand its range further in 300,000 years than Homo erectus did in 1.5 million years? The key is the set of derived biological traits from the last section. It is theorized that the gracile frame and neurological anatomy allowed modern humans to survive and even flourish in the vastly different environments they encountered. Based on multiple types of evidence, the source of all of these modern humans was Africa. Instead of originating from just one location, evidence shows that modern Homo sapiens evolution occurred in a complex gene flow network across Africa, a concept called African multiregionalism (Scerri et al. 2018).
This section traces the origin of modern Homo sapiens and the massive expansion of our species across all of the continents (except Antarctica) by 12,000 years ago. While modern Homo sapiens first shared geography with archaic humans, modern humans eventually spread into lands where no human had gone before. Figure 13.5 shows the broad routes that our species took expanding around the world. I encourage you to make your own timeline with the dates in this part to see the overall trends.
Modern Homo sapiens Biology and Culture in Africa
We start with the ample fossil evidence supporting the theory that modern humans originated in Africa during the Middle Pleistocene, having evolved from African archaic Homo sapiens. The earliest dated fossils considered to be modern actually have a mosaic of archaic and modern traits, showing the complex changes from one type to the other. Experts have various names for these transitional fossils, such as Early Modern Homo sapiens or Early Anatomically Modern Humans. However they are labeled, the presence of some modern traits means that they illustrate the origin of the modern type. Three particularly informative sites with fossils of the earliest modern Homo sapiens are Jebel Irhoud, Omo, and Herto.
Recall from the start of the chapter that the most recent finds at Jebel Irhoud are now the oldest dated fossils that exhibit some facial traits of modern Homo sapiens. Besides Irhoud 10, the cranium that was dated to 315,000 years ago (Hublin et al. 2017; Richter et al. 2017), there were other fossils found in the same deposit that we now know are from the same time period. In total there are at least five individuals, representing life stages from childhood to adulthood. These fossils form an image of high variation in skeletal traits. For example, the skull named Irhoud 1 has a primitive brow ridge, while Irhoud 2 and Irhoud 10 do not (Figure 13.6). The braincases are lower than what is seen in the modern humans of today but higher than in archaic Homo sapiens. The teeth also have a mix of archaic and modern traits that defy clear categorization into either group.
Research separated by nearly four decades uncovered fossils and artifacts from the Kibish Formation in the Lower Omo Valley in Ethiopia. These Omo Kibish hominins were represented by braincases and fragmented postcranial bones of three individuals found kilometers apart, dating back to around 233,000 years ago (Day 1969; McDougall, Brown, and Fleagle 2005; Vidal et al. 2022). One interesting finding was the variation in braincase size between the two more-complete specimens: while the individual named Omo I had a more globular dome, Omo II had an archaic-style long and low cranium.
Also in Ethiopia, a team led by Tim White (2003) excavated numerous fossils at Herto. There were fossilized crania of two adults and a child, along with fragments of more individuals. The dates ranged between 160,000 and 154,000 years ago. The skeletal traits and stone-tool assemblage were both intermediate between the archaic and modern types. Features reminiscent of modern humans included a tall braincase and thinner zygomatic (cheek) bones than those of archaic humans (Figure 13.7). Still, some archaic traits persisted in the Herto fossils, such as the supraorbital tori. Statistical analysis by other research teams concluded that at least some cranial measurements fit just within the modern human range (McCarthy and Lucas 2014), favoring categorization with our own species.
The timeline of material culture suggests a long period of relying on similar tools before a noticeable diversification of artifacts types. Researchers label the time of stable technology shared with archaic types the Middle Stone Age, while the subsequent time of diversification in material culture is called the Later Stone Age.
In the Middle Stone Age, the sites of Jebel Irhoud, Omo, and Herto all bore tools of the same flaked style as archaic assemblages, even though they were separated by almost 150,000 years. The consistency in technology may be evidence that behavioral modernity was not so developed. No clear signs of art dating back this far have been found either. Other hypotheses not related to behavioral modernity could explain these observations. The tool set may have been suitable for thriving in Africa without further innovation. Maybe works of art from that time were made with media that deteriorated or perhaps such art was removed by later humans.
Evidence of what Homo sapiens did in Africa from the end of the Middle Stone Age to the Later Stone Age is concentrated in South African cave sites that reveal the complexity of human behavior at the time. For example, Blombos Cave, located along the present shore of the Cape of Africa facing the Indian Ocean, is notable for having a wide variety of artifacts. The material culture shows that toolmaking and artistry were more complex than previously thought for the Middle Stone Age. In a layer dated to 100,000 years ago, researchers found two intact ochre-processing kits made of abalone shells and grinding stones (Henshilwood et al. 2011). Marine snail shell beads from 75,000 years ago were also excavated (Figure 13.8; d’Errico et al. 2005). Together, the evidence shows that the Middle Stone Age occupation at Blombos Cave incorporated resources from a variety of local environments into their culture, from caves (ochre), open land (animal bones and fat), and the sea (abalone and snail shells). This complexity shows a deep knowledge of the region’s resources and their use—not just for survival but also for symbolic purposes.
On the eastern coast of South Africa, Border Cave shows new African cultural developments at the start of the Later Stone Age. Paola Villa and colleagues (2012) identified several changes in technology around 43,000 years ago. Stone-tool production transitioned from a slower process to one that was faster and made many microliths, small and precise stone tools. Changes in decorations were also found across the Later Stone Age transition. Beads were made from a new resource: fragments of ostrich eggs shaped into circular forms resembling present-day breakfast cereal O’s (d’Errico et al. 2012). These beads show a higher level of altering one’s own surroundings and a move from the natural to the abstract in terms of design.
Expansion into the Middle East and Asia
While modern Homo sapiens lived across Africa, some members eventually left the continent. These pioneers could have used two connections to the Middle East or West Asia. From North Africa, they could have crossed the Sinai Peninsula and moved north to the Levant, or eastern Mediterranean. Finds in that region show an early modern human presence. Other finds support the Southern Dispersal model, with a crossing from East Africa to the southern Arabian Peninsula through the Straits of Bab-el-Mandeb. It is tempting to think of one momentous event in which people stepped off Africa and into the Middle East, never to look back. In reality, there were likely multiple waves of movement producing gene flow back and forth across these regions as the overall range pushed east. The expanding modern human population could have thrived by using resources along the southern coast of the Arabian Peninsula to South Asia, with side routes moving north along rivers. The maximum range of the species then grew across Asia.
Modern Homo sapiens in the Middle East
Geographically, the Middle East is the ideal place for the African modern Homo sapiens population to inhabit upon expanding out of their home continent. In the Eastern Mediterranean coast of the Levant, there is a wealth of skeletal and material culture linked to modern Homo sapiens. Recent discoveries from Saudi Arabia further add to our view of human life just beyond Africa.
The Caves of Mount Carmel in present-day Israel have preserved skeletal remains and artifacts of modern Homo sapiens, the first-known group living outside Africa. The skeletal presence at Misliya Cave is represented by just part of the left upper jaw of one individual, but it is notable for being dated to a very early time, between 194,000 and 177,000 years ago (Hershkovitz et al. 2018). Later, from 120,000 to 90,000 years ago, fossils of multiple individuals across life stages were found in the caves of Es-Skhul and Qafzeh (Shea and Bar-Yosef 2005). The skeletons had many modern Homo sapiens traits, such as globular crania and more gracile postcranial bones when compared to Neanderthals. Still, there were some archaic traits. For example, the adult male Skhul V also possessed what researchers Daniel Lieberman, Osbjorn Pearson, and Kenneth Mowbray (2000) called marked or clear occipital bunning. Also, compared to later modern humans, the Mount Carmel people were more robust. Skhul V had a particularly impressive brow ridge that was short in height but sharply jutted forward above the eyes (Figure 13.9). The high level of preservation is due to the intentional burial of some of these people. Besides skeletal material, there are signs of artistic or symbolic behavior. For example, the adult male Skhul V had a boar’s jaw on his chest. Similarly, Qafzeh 11, a juvenile with healed cranial trauma, had an impressive deer antler rack placed over his torso (Figure 13.10; Coqueugniot et al. 2014). Perforated seashells colored with ochre, mineral-based pigment, were also found in Qafzeh (Bar-Yosef Mayer, Vandermeersch, and Bar-Yosef 2009).
One remaining question is, what happened to the modern humans of the Levant after 90,000 years ago? Another site attributed to our species did not appear in the region until 47,000 years ago. Competition with Neanderthals may have accounted for the disappearance of modern human occupation since the Neanderthal presence in the Levant lasted longer than the dates of the early modern Homo sapiens. John Shea and Ofer Bar-Yosef (2005) hypothesized that the Mount Carmel modern humans were an initial expansion from Africa that failed. Perhaps they could not succeed due to competition with the Neanderthals who had been there longer and had both cultural and biological adaptations to that environment.
Modern Homo sapiens of China
A long history of paleoanthropology in China has found ample evidence of modern human presence. Four notable sites are the caves at Fuyan, Liujiang, Tianyuan, and Zhoukoudian. In the distant past, these caves would have been at least seasonal shelters that unintentionally preserved evidence of human presence for modern researchers to discover.
At Fuyan Cave in Southern China, paleoanthropologists found 47 adult teeth associated with cave formations dated to between 120,000 and 80,000 years ago (Liu et al. 2015). It is currently the oldest-known modern human site in China, though other researchers question the validity of the date range (Michel et al. 2016). The teeth have the small size and gracile features of modern Homo sapiens dentition.
The fossil Liujiang (or Liukiang) hominin (67,000 years ago) has derived traits that classified it as a modern Homo sapiens, though primitive archaic traits were also present. In the skull, which was found nearly complete, the Liujiang hominin had a taller forehead than archaic Homo sapiens but also had an enlarged occipital region (Figure 13.11; Brown 1999; Wu et al. 2008). Other parts of the skeleton also had a mix of modern and archaic traits: for example, the femur fragments suggested a slender length but with thick bone walls (Woo 1959).
Another Chinese site to describe here is the one that has been studied the longest. In the Zhoukoudian Cave system (Figure 13.12), where Homo erectus and archaic Homo sapiens have also been found, there were three crania of modern Homo sapiens. These crania, which date to between 34,000 and 10,000 years ago, were all more globular than those of archaic humans but still lower and longer than those of later modern humans (Brown 1999; Harvati 2009). When compared to one another, the crania showed significant differences from one another. Comparison of cranial measurements to other populations past and present found no connection with modern East Asians, again showing that human variation was very different from what we see today.
Crossing to Australia
Expansion of the first modern human Asians, still following the coast, eventually entered an area that researchers call Sunda before continuing on to modern Australia. Sunda was a landmass made up of the modern-day Malay Peninsula, Sumatra, Java, and Borneo. Lowered sea levels connected these places with land bridges, making them easier to traverse. Proceeding past Sunda meant navigating Wallacea, the archipelago that includes the Indonesian islands east of Borneo. In the distant past, there were many megafauna, large animals that migrating humans would have used for food and materials (such as utilizing animals’ hides and bones). Further southeast was another landmass called Sahul, which included New Guinea and Australia as one contiguous continent. Based on fossil evidence, this land had never seen hominins or any other primates before modern Homo sapiens arrived. Sites along this path offer clues about how our species handled the new environment to live successfully as foragers.
The skeletal remains at Lake Mungo, land traditionally owned by Mutthi Mutthi, Ngiampaa, and Paakantji peoples, are the oldest known in the continent. The now-dry lake was one of a series located along the southern coast of Australia in New South Wales, far from where the first people entered from the north (Barbetti and Allen 1972; Bowler et al. 1970). Two individuals dating to around 40,000 years ago show signs of artistic and symbolic behavior, including intentional burial. The bones of Lake Mungo 1 (LM1), an adult female, were crushed repeatedly, colored with red ochre, and cremated (Bowler et al. 1970). Lake Mungo 3 (LM3), a tall, older male with a gracile cranium but robust postcranial bones, had his fingers interlocked over his pelvic region (Brown 2000).
Kow Swamp, within traditional Yorta Yorta land also in southern Australia, contained human crania that looked distinctly different from the ones at Lake Mungo (Durband 2014; Thorne and Macumber 1972). The crania, dated between 9,000 and 20,000 years ago, had extremely robust brow ridges and thick bone walls, but these were paired with globular features on the braincase (Figure 13.13).
While no fossil humans have been found at the Madjedbebe rock shelter in the North Territory of Australia, more than 10,000 artifacts found there show both behavioral modernity and variability (Clarkson et al. 2017). They include a diverse array of stone tools and different shades of ochre for rock art, including mica-based reflective pigment (similar to glitter). These impressive artifacts are as far back as 56,000 years old, providing the date for the earliest-known presence of humans in Australia.
From the Levant to Europe
The first modern human expansion into Europe occurred after other members of our species settled in East Asia and Australia. As the evidence from the Levant suggests, modern human movement to Europe may have been hampered by the presence of Neanderthals. It is suggested that another obstacle was the colder climate, which was incompatible with the biology of modern Homo sapiens from Africa, as they were adapted to high temperatures and ultraviolet radiation. Still, by 40,000 years ago, modern Homo sapiens had a detectable presence. This time was also the start of the Later Stone Age or Upper Paleolithic, when there was an expansion in cultural complexity. There is a wealth of evidence from this region due to a Western bias in research, the proximity of these findings to Western scientific institutions, and the desire of Western scientists to explore their own past.
In Romania, the site of Peștera cu Oase (Cave of Bones) had the oldest-known remains of modern Homo sapiens in Europe, dated to around 40,000 years ago (Trinkaus et al. 2003a). Among the bones and teeth of many animals were the fragmented cranium of one person and the mandible of another (the two bones did not fit each other). Both bones have modern human traits similar to the fossils from the Middle East, but they also had Neanderthal traits. Oase 1, the mandible, had a mental eminence but also extremely large molars (Trinkaus et al. 2003b). This mandible has yielded DNA that surprisingly is equally similar to DNA from present-day Europeans and Asians (Fu et al. 2015). This means that Oase 1 was not the direct ancestor of modern Europeans. The Oase 2 cranium has the derived traits of reduced brow ridges along with archaic wide zygomatic cheekbones and an occipital bun (Figure 13.14; Rougier et al. 2007).
Dating to around 26,000 years ago, Předmostí near Přerov in the Czech Republic was a site where people buried over 30 individuals along with many artifacts. Eighteen individuals were found in one mass burial area, a few covered by the scapulae of woolly mammoths (Germonpré, Lázničková-Galetová, and Sablin 2012). The Předmostí crania were more globular than those of archaic humans but tended to be longer and lower than in later modern humans (Figure 13.15; Velemínská et al. 2008). The height of the face was in line with modern residents of Central Europe. There was also skeletal evidence of dog domestication, such as the presence of dog skulls with shorter snouts than in wild wolves (Germonpré, Lázničková-Galetová, and Sablin et al. 2012). In total, Předmostí could have been a settlement dependent on mammoths for subsistence and the artificial selection of early domesticated dogs.
The sequence of modern Homo sapiens technological change in the Later Stone Age has been thoroughly dated and labeled by researchers working in Europe. Among them, the Gravettian tradition of 33,000 years to 21,000 years ago is associated with most of the known curvy female figurines, often assumed to be “Venus” figures. Hunting technology also advanced in this time with the first known boomerang, atlatl (spear thrower), and archery. The Magdalenian tradition spread from 17,000 to 12,000 years ago. This culture further expanded on fine bone tool work, including barbed spearheads and fishhooks (Figure 13.16).
Among the many European sites dating to the Later Stone Age, the famous cave art sites deserve mention. Chauvet-Pont-d'Arc Cave in southern France dates to separate Aurignacian occupations 31,000 years ago and 26,000 years ago. Over a hundred art pieces representing 13 animal species are preserved, from commonly depicted deer and horses to rarer rhinos and owls. Another French cave with art is Lascaux, which is several thousand years younger at 17,000 years ago in the Magdalenian period. At this site, there are over 6,000 painted figures on the walls and ceiling (Figure 13.17). Scaffolding and lighting must have been used to make the paintings on the walls and ceiling deep in the cave. Overall, visiting Lascaux as a contemporary must have been an awesome experience: trekking deeper in the cave lit only by torches giving glimpses of animals all around as mysterious sounds echoed through the galleries.
Special Topic: Cannibalism and Culture - Mortuary Practices in Modern Homo sapiens.
Within a 2017 publication in the Journal of Archaeological Method and Theory, Saladié and Rodríguez-Hidalgo bring light to traces of early cannibalism in western Eurasia, arguing that context-specific cannibalistic practices were present throughout the Pleistocene and increased notably from the end of the Upper Palaeolithic and onward (Saladié & Rodriguez-Hidalgo, 2017). While early hominins and Neandertals are recognized in this research, the authors highlight the presence of these mortuary practices in a cluster of Homo Sapien sites. More recent research uncovers similar findings that back these claims as well, where human bones in Herto Ethiopia, Maszycka Cave Poland, and Gough’s Cave in the United Kingdom show anthropogenic defleshing and other modifications which have been interpreted as cannibalism (Pobiner, Et al. 2023). These findings suggest that cannibalistic behaviours formed a recurring aspect of modern human behaviour in certain ecological and cultural contexts.
A significant example comes from the Neolithic levels of Fontbrégua Cave in southeastern France, where Paola Villa and colleagues compared clusters of human bones with the remains of wild and domestic animals from the same sediments. The study found that human bodies were butchered, processed, and most likely eaten in a way that parallels animal carcass treatment, including the placement and timing of cut marks, dismemberment sequences, and perimortem fractures to open marrow cavities (Villa, Et al. 1986). As the assemblage comes from a primary depositional context with pristine preservation and careful excavation, the authors suggest that cannibalism is the only satisfactory explanation for the pattern of cut marks and breakage seen on the human bones.
More recent work has furthered this hypothesis for Late Upper Palaeolithic Homo sapiens, especially in Magdalenian contexts. In a 2023 study, researchers combined archeological and genetic evidence from fifty-nine Magdalenian sites, concluding that this specific culture shows an unusually high frequency of cannibalistic cases compared to earlier and later hominin groups; so much so that they identify “primary burial and cannibalism” as the two main mortuary expressions (Marsh & Bello, 2023). Additionally, new analyses from Maszycka Cave in Poland have described cut and broken human bones in patterns consistent with human consumption, reinforcing this cannibalism hypothesis (Marginedas & Saladié, 2025). Together, these studies suggest that for some Magdalenian groups, mortuary cannibalism was a habitual way of disposing of the dead, not just a one-off crisis response. At the same time, researchers emphasize that not every modified skeleton indicates blatant consumption of the dead and that ritual or symbolic perspectives must also be considered. Previously noted in chapter eleven, Ullrich’s survey of European mortuary practices presents frequent manipulations of corpses from the Palaeolithic through the Hallstatt period. Said manipulations include cut marks, dismemberment, skull fracturing, and marrow extraction (Ullrich, 2005, p. 258), which Ullrich interprets as cannibalistic rites embedded in cult ceremonies rather than everyday subsistence. In the author’s view, some Palaeolithic groups may have believed that consuming members of their community allowed them to take on the strengths, abilities, or even mental aspects of their dead member; the act of cannibalism may have functioned as a form of appropriating physical and mental powers rather than simply obtaining calories. With that, Neolithic assemblages show how careful taphonomic work can distinguish cuts linked to interpersonal violence from those associated with systemic butchery (Marginedas & Saladié, 2025). The findings seek to highlight that some Homo sapiens populations combined ritual, mortuary, and nutritional motives when processing human remains.
These past and contemporary findings are significant for future anthropology students as they shed light on biological anthropology methodology and interpretation. Archaeologists are able to distinguish between occasions when humans were handled like any other carcass and times when they were handled in more symbolic ways thanks to factors like cut mark orientation, the timing of bone breakage, and direct comparison with animal remains. Readers interested in exploring this topic further should investigate the context-specific motivations for cannibalism, like nutritional stress, warfare, funerary sites, or ritual power appropriation.
Similar archeological techniques have been used to explore behaviours of cannibalism among Indigenous Huron-Wendat populations in 1651 Canada, where human bones exhibit cutmarks, perimortem fractures, and thermal modifications (Spence & Jackson, 2014). These shared taphonomic signatures across continents reveal recurring practices under ecological stress, bridging prehistoric Europe to North American contexts. Engaging with such analytical techniques opens up new ways that archeologists and anthropologists can investigate the variability in human behaviour, from nutritional crises to mortuary rituals.
Peopling of the Americas
By 25,000 years ago, our species was the only member of Homo left on Earth. Gone were the Neanderthals, Denisovans, Homo naledi, and Homo floresiensis. The range of modern Homo sapiens kept expanding eastward into—using the name given to this area by Europeans much later—the Western Hemisphere. This section will address what we know about the peopling of the Americas, from the first entry to these continents to the rapid spread of Indigenous Americans across its varied environments.
While evidence points to an ancient land bridge called Beringia that allowed people to cross from what is now northeastern Siberia into modern-day Alaska, what people did to cross this land bridge is still being investigated. For most of the 20th century, the accepted theory was the Ice-Free Corridor model. It stated that northeast Asians (East Asians and Siberians) first expanded across Beringia inland through a passage between glaciers that opened into the western Great Plains of the United States, just east of the Rocky Mountains, around 13,000 years ago (Swisher et al. 2013). While life up north in the cold environment would have been harsh, migrating birds and an emerging forest might have provided sustenance as generations expanded through this land (Potter et al. 2018).
However, in recent decades, researchers have accumulated evidence against the Ice-Free Corridor model. Archaeologist K. R. Fladmark (1979) brought the alternate Coastal Route model into the archaeological spotlight; researcher Jon M. Erlandson has been at the forefront of compiling support for this theory (Erlandson et al. 2015). The new focus is the southern edge of the land bridge instead of its center: About 16,000 years ago, members of our species expanded along the coastline from northeast Asia, east through Beringia, and south down the Pacific Coast of North America while the inland was still sealed off by ice. The coast would have been free of ice at least part of the year, and many resources would have been found there, such as fish (e.g., salmon), mammals (e.g., whales, seals, and otters), and plants (e.g., seaweed).
South through the Americas
When the first modern Homo sapiens reached the Western Hemisphere, the spread through the Americas was rapid. Multiple migration waves crossed from North to South America (Posth et al. 2018). Our species took advantage of the lack of hominin competition and the bountiful resources both along the coasts and inland. The Americas had their own wide array of megafauna, which included woolly mammoths (Figure 13.18), mastodons, camels, horses, ground sloths, giant tortoises, and—a favorite of researchers—a two-meter-tall beaver. The reason we cannot see these amazing animals today may be that resources gained from these fauna were crucial to the survival for people over 12,000 years ago (Araujo et al. 2017). Several sites are notable for what they add to our understanding of the distant past in the Americas, including interactions with megafauna and other elements of the environment.
A 2019 discovery may allow researchers to improve theories about the peopling of the Americas. In White Sands National Park, New Mexico, 60 human footprints have been astonishingly dated to around 22,000 years ago (Bennett et al. 2021). This date and location do not match either the Ice-Free Corridor or Coastal Route models. Researchers are now working to verify the find and adjust previous models to account for the new evidence. This groundbreaking find is sparking new theories; it is another example of the fast pace of research performed on our past.
Monte Verde is a landmark site that shows that the human population had expanded down the whole vertical stretch of the Americas to Chile by 14,600 years ago. The site has been excavated by archaeologist Tom D. Dillehay and his team (2015). The remains of nine distinct edible species of seaweed at the site shows familiarity with coastal resources and relates to the Coastal Route model by showing a connection between the inland people and the sea.
Named after the town in New Mexico, the Clovis stone-tool style is the first example of a widespread culture across much of North America, between 13,400 and 12,700 years ago (Miller, Holliday, and Bright 2013). Clovis points were fluted with two small projections, one on each end of the base, facing away from the head (Figure 13.19). The stone points found at this site match those found as far as the Canadian border and northern Mexico, and from the west coast to the east coast of the United States. Fourteen Clovis sites also contained the remains of mammoths or mastodons, suggesting that hunting megafauna with these points was an important part of life for the Clovis people. After the spread of the Clovis style, it diversified into several regional styles, keeping some of the Clovis form but also developing their own unique touches.
The Big Picture: The Assimilation Hypothesis
How do researchers make sense of all of these modern Homo sapiens discoveries that cover over 300,000 years of time and stretch across every continent except Antarctica? How was modern Homo sapiens related to archaic Homo sapiens?
The Assimilation hypothesis proposes that modern Homo sapiens evolved in Africa first and expanded out but also interbred with the archaic Homo sapiens they encountered outside Africa (Figure 13.20). This hypothesis is powerful since it explains why Africa has the oldest modern human fossils, why early modern humans found in Europe and Asia bear a resemblance to the regional archaics, and why traces of archaic DNA can be found in our genomes today (Dannemann and Racimo 2018; Reich et al. 2010; Reich et al. 2011; Slatkin and Racimo 2016; Smith et al. 2017; Wall and Yoshihara Caldeira Brandt 2016).
While researchers have produced a model that satisfies the data, there are still a lot of questions for paleoanthropologists to answer regarding our origins. What were the patterns of migration in each part of the world? Why did the archaic humans go extinct? In what ways did archaic and modern humans interact? The definitive explanation of how our species started and what our ancestors did is still out there to be found. You are now in a great place to welcome the next discovery about our distant past—maybe you’ll even contribute to our understanding as well.
The Chain Reaction of Agriculture
While it may be hard to imagine today, for most of our species’ existence we were nomadic: moving through the landscape without a singular home. Instead of a refrigerator or pantry stocked with food, we procured nutrition and other resources as needed based on what was available in the environment. This section gives an overview of how the foraging lifestyle enabled the expansion of our species and how the invention of a new way of life caused a chain reaction of cultural change.
The Foraging Tradition
There are a variety of possible subsistence strategies, or methods of finding sustenance and resources. To understand our species is to understand the subsistence strategy of foraging, or the search for resources in the environment. While most (but not all) humans today live in cultures that practice agriculture (whereby we greatly shape the environment to mass produce what we need), we have spent far more time as nomadic foragers than as settled agriculturalists. As such, it has been suggested that our traits have evolved to be primarily geared toward foraging. For instance, our efficient bipedalism allows persistence-hunting across long distances as well as movement from resource to resource.
How does human foraging, also known as hunting and gathering, work? Anthropologists have used all four fields to answer this question (see Ember n.d.). Typically, people formed bands, or kin-based groups of around 50 people or less (rarely over 100). A band’s organization would be egalitarian, with a flexible hierarchy based on an individual’s age, level of experience, and relationship with others. Everyone would have a general knowledge of the skills assigned to their gender roles, rather than specializing in different occupations. A band would be able to move from place to place in the environment, using knowledge of the area to forage (Figure 13.21). In varied environments—from savannas to tropical forests, deserts, coasts, and the Arctic circle—people found sustenance needed for survival.
Humans made extensive use of the foraging subsistence strategy, but this lifestyle did have limitations. The ease of foraging depended on the richness of the environment. Due to the lack of storage, resources had to be dependably found when needed. While a bountiful environment would require just a few hours of foraging a day and could lead to a focus on one location, the level and duration of labor increased greatly in poor or unreliable environments. Labor was also needed to process the acquired resources, which contributed to the foragers’ daily schedule (Crittenden and Schnorr 2017).
The adaptations to foraging found in modern Homo sapiens may explain why our species became so successful both within Africa and in the rapid expansion around the world. Overcoming the limitations, each generation at the edge of our species’s range would have found it beneficial to expand a little further, keeping contact with other bands but moving into unexplored territory where resources were more plentiful. The cumulative effect would have been the spread of modern Homo sapiens across continents and hemispheres.
Why Agriculture?
After hundreds of thousands of years of foraging, some groups of people around 12,000 years ago started to practice agriculture. This transition, called the Neolithic Revolution, occurred at the start of the Holocene epoch. While the reasons for this global change are still being investigated, two likely co-occurring causes are a growing human population and natural global climate change.
Overcrowding could have affected the success of foraging in the environment, leading to the development of a more productive subsistence strategy (Cohen 1977). Foraging works best with low population densities since each band needs a lot of space to support itself. If too many people occupy the same environment, they deplete the area faster. The high population could exceed the carrying capacity, or number of people a location can reliably support. Reaching carrying capacity on a global level due to growing population and limited areas of expansion would have been an increasingly pressing issue after the expansion through the major continents by 14,600 years ago.
A changing global climate immediately preceded the transition to agriculture, so researchers have also explored a connection between the two events. Since the Last Glacial Maximum of 23,000 years ago, the Earth slowly warmed. Then, from 13,000 to 11,700 years ago, the temperature in most of the Northern Hemisphere dropped suddenly in a phenomenon called the Younger Dryas. Glaciers returned in Europe, Asia, and North America. In Mesopotamia, which includes the Levant, the climate changed from warm and humid to cool and dry. The change would have occurred over decades, disrupting the usual nomadic patterns and subsistence of foragers around the world. The disruption to foragers due to the temperature shift could have been a factor in spurring a transition to agriculture. Researchers Gregory K. Dow and colleagues (2009) believe that foraging bands would have clustered in the new resource-rich places where people started to direct their labor to farming the limited area. After the Younger Dryas ended, people expanded out of the clusters with their agricultural knowledge (Figure 13.22).
The double threat of the limitation of human continental expansion and the sudden global climate change may have placed bands in peril as more populations outpaced their environment’s carrying capacity. Not only had a growing population led to increased competition with other bands, but environments worldwide had shifted to create more uncertainty. As such, it has been proposed that as people in different areas around the world faced this unpredictable situation, they became the independent inventors of agriculture.
Agriculture around the World
Due to global changes to the human experience starting from 12,000 years ago, it has been suggested that cultures with no knowledge of each other turned toward intensely farming their local resources (see Figure 13.22). It is proposed that the first farmers engaged in artificial selection of their domesticates to enhance useful traits over generations. The switch to agriculture took time and effort with no guarantee of success and constant challenges (e.g. fires, droughts, diseases, and pests). The regions with the most widespread impact in the face of these obstacles became the primary centers of agriculture (Figure 13.23; Fuller 2010):
- Mesopotamia: The Fertile Crescent from the Tigris and Euphrates rivers through the Levant was where bands started to domesticate plants and animals around 12,000 years ago. The connection between the development of agriculture and the Younger Dryas was especially strong here. Farmed crops included wheat, barley, peas, and lentils. This was also where cattle, pigs, sheep, and goats were domesticated.
- South and East Asia: Multiple regions across this land had varieties of rice, millet, and soybeans by 10,000 years ago. Pigs were farmed with no connection to Mesopotamia. Chickens were also originally from this region, bred for fighting first and food second.
- New Guinea: Agriculture started here 10,000 years ago. Bananas, sugarcane, and taro were native to this island. Sweet potatoes were brought back from voyages to South America around the year C.E. 1000. No known animal farming occurred here.
- Mesoamerica: Agriculture from Central Mexico to northern South America also occurred from 10,000 years ago; it was also only plant based. Maize was a crop bred from teosinte grass, which has become one of the global staples. Beans, squash, and avocados were also grown in this region.
- The Andes: Starting around 8,000 years ago, local domesticated plants started with squash but later included potatoes, tomatoes, beans, and quinoa. Maize was brought down from Mesoamerica. The main farm animals were llamas, alpacas, and guinea pigs.
- Sub-Saharan Africa: This region went through a change 5,000 years ago called the Bantu expansion. The Bantu agriculturalists were established in West Central Africa and then expanded south and east. Native varieties of rice, yams, millet, and sorghum were grown across this area. Cattle were also domesticated here.
- Eastern North America: This region was the last major independent agriculture center, from 4,000 years ago. Squash and sunflower are the produce from this region that are most known today, though sumpweed and pitseed goosefoot were also farmed. Hunting was still the main source of animal products.
By 5,000 years ago, our species was well within the Neolithic Revolution. Agriculturalists spread to neighboring parts of the world with their domesticates, further expanding the use of this subsistence strategy. From this point, the human species changed from being primarily foragers to primarily agriculturalists with skilled control of their environments. The planet changed from mostly unaffected by human presence to being greatly transformed by humans. The revolution took millennia, but it was a true revolution as our species’ lifestyle was dramatically reshaped.
Cultural Effects of Agriculture
The worldwide adoption of agriculture altered the course of human culture and history forever. The core change in human culture due to agriculture is the move toward not moving: rather than live a nomadic lifestyle, farmers had to remain in one area to tend to their crops and livestock. The term for living bound to a certain location is sedentarism. This led to new aspects of life that were uncommon among foragers: the construction of permanent shelters and agricultural infrastructure, such as fields and irrigation, plus the development of storage technology, such as pottery, to preserve extra resources in case of future instability.
The high productivity of successful agriculture sparked further changes (Smith 2009). It is argued that since successful agriculture produced a much greater amount of food and other resources per unit of land compared to foraging, the population growth rate skyrocketed. The surplus of a bountiful harvest also provided insurance for harder times, reducing the risk of famine. Changes happened to society as well. With a few farming households producing enough food to feed many others, other people could focus on other tasks. So began specialization into different occupations such as craftspeople, traders, religious figures, and artists, spurring innovation in these areas as people could now devote time and effort toward specific skills. These interdependent people would settle an area together for convenience. The growth of these settlements led to urbanization, the founding of cities that became the foci of human interaction (Figure 13.24).
The formation of cities led to new issues that sparked the growth of further specializations, called institutions. These are cultural constructs that exist beyond the individual and have wide control over a population. Leadership of these cities became hierarchical with different levels of rank and control. The stratification of society increased social inequality between those with more or less power over others. Under leadership, people built impressive monumental architecture, such as pyramids and palaces, that embodied the wealth and power of these early cities. Alliances could unite cities, forming the earliest states. In several regions of the world, state organization expanded into empires, wide-ranging political entities that covered a variety of cultures.
Urbanization brought new challenges as well. The concentration of sedentary peoples was ideal for infectious diseases to thrive since they could jump from person to person and even from livestock to person (Armelagos, Brown, and Turner 2005). While successful agriculture provided a large surplus of food to thwart famine, the food produced offered less diverse food sources than foragers’ diets (Cohen and Armelagos 1984; Cohen and Crane-Kramer 2007). This shift in nutrition caused other diseases to flourish among those who adopted farming, such as dental cavities and malocclusion (the misalignment of teeth caused by soft, agricultural diets). The need to extract “wisdom teeth” or third molars seen in agricultural cultures today stems from this misalignment between the environment our ancestors adapted to and our lifestyles today.
As the new disease trends show, the adoption of agriculture and the ensuing cultural changes were not entirely positive. It is also important to note that this is not an absolutely linear progression of human culture from simple to complex. In many cases, empires have collapsed and, in some cases, cities dispersed to low-density bands that rejected institutions. However, a global trend has emerged since the adoption of agriculture, wherein population and social inequality have increased, leading to the massive and influential nation-states of today.
The rise of states in Europe has a direct impact on many of this book’s topics. Science started as a European cultural practice by the upper class that became a standardized way to study the world. Education became an institution to provide a standardized path toward producing and gaining knowledge. The scientific study of human diversity, embroiled in the race concept that still haunts us today, was connected to the European slave trade and colonialism.
Also starting in Europe, the Industrial Revolution of the 19th century turned cities into centers of mass manufacturing and spurred the rapid development of inventions (Figure 13.25). In the technologically interconnected world of today, human society has reached a new level of complexity with globalization. In this system, goods are mass-produced and consumed in different parts of the world, weakening the reliance on local farms and factories. The imbalanced relationship between consumers and producers of goods further increases economic inequality.
As states based on agriculture and industry keep exerting influence on humanity today, there are people, like the Hadzabe of Tanzania, who continue to live a lifestyle centered on foraging. Due to the overwhelming force that agricultural societies exert, foragers today have been marginalized to live in the least habitable parts of the world—the areas that are not conducive to farming, such as tropical rainforests, deserts, and the Arctic (Headland et al. 1989). Foragers can no longer live in the abundant environments that humans would have enjoyed before the Neolithic Revolution. Interactions with agriculturalists are typically imbalanced, with trade and other exchanges heavily favoring the larger group. One of anthropology’s important roles today is to intelligently and humanely manage equitable interactions between people of different backgrounds and levels of influence.
Special Topic: Indigenous Land Management
Insight into the lives of past modern humans has evolved as researchers revise previous theories and establish new connections with Indigenous knowledge holders.
The outdated view of foraging held that people lived off of the land without leaving an impact on the environment. Accompanying this idea was anthropologist Marshall Sahlins’s (1968) proposal that foragers were the “original affluent society” since they were meeting basic needs and achieving satisfaction with less work hours than agriculturalists and city-dwellers. This view countered an earlier idea that foragers were always on the brink of starvation. Sahlins’s theory took hold in the public eye as an attractive counterpoint to our busy contemporary lives in which we strive to meet our endless wants.
A fruitful type of study involving researchers collaborating with Indigenous experts has found that foragers did not just live off the land with minimal effort nor were they barely surviving in unchanging environments. Instead, they shaped the landscape to their needs using labor and strategies that were more subtle than what European colonizers and subsequent researchers were used to seeing. Research from two regions shows the latest developments in understanding Indigenous land management.
In British Columbia, Canada, the bridging of scientific and Indigenous perspectives has shown that the forests of the region are not untouched wilderness but, rather, have been crafted by Indigenous peoples thousands of years ago. Forest gardens adjacent to archaeological sites show higher plant diversity than unmanaged places even after 150 years (Armstrong et al. 2021). On the coast, 3,500-year-old archaeological sites are evidence of constructed clam gardens, according to Indigenous experts (Lepofsky et al. 2015). Another project, in consultation with Elders of the T’exelc (William Lakes First Nation) in British Columbia, introduced researchers to explanations of how forests were managed before the practice was disrupted by European colonialism (Copes-Gerbitz et al. 2021). Careful management of controlled fires reduced the density of the forest to favor plants such as raspberries and allow easier movement through the landscape.
Similarly, the study of landscapes in Australia, in consultation with Aboriginal Australians today, shows that areas previously considered wilderness by scientists were actually the result of controlling fauna and fires. The presence of grasslands with adjacent forests were purposely constructed to attract kangaroos for hunting (Gammage 2008). People also managed other animal and insect life, from emus to caterpillars. In Tasmania, a shift from productive grassland to wildfire-prone rainforest occurred after Aboriginal Australian land management was replaced by British colonial rule (Fletcher, Hall, and Alexander 2021). The site of Budj Bim of the Gunditjmara people has archaeological features of aquaculture, or the farming of fish, that date back 6,600 years (McNiven et al. 2012; McNiven et al. 2015). These examples show that Indigenous knowledge of how to manipulate the environment may be invaluable at the state level, such as by creating an Aboriginal ranger program to guide modern land management.
The Future of Humanity
A common question stemming from understanding human evolution is: What will the genetic and biological traits of our species be hundreds of thousands of years in the future? When faced with this question, people tend to think of directional selection. Maybe our braincases will be even larger, resembling the large-headed and small-bodied aliens of science fiction (Figure 13.26). Or, our hands could be specialized for interacting with our touch-based technology with less risk of repetitive injury. These ideas do not stand up to scrutiny. Since natural selection is based on adaptations that increase reproductive success, any directional change must be due to a higher rate of producing successful offspring compared to other alleles. Larger brains and more agile fingers would be convenient to possess, but they do not translate into an increase in the underlying allele frequencies.
Scientists are hesitant to professionally speculate on the unknowable, and we will never know what is in store for our species one thousand or one million years from now, but there are two trends in human evolution that may carry on into the future: increased genetic variation and a reduction in regional differences.
Rather than a directional change, genetic variation in our species could expand. Our technology can protect us from extreme environments and pathogens, even if our biological traits are not tuned to handle these stressors. The rapid pace of technological advancement means that biological adaptations will become less and less relevant to reproductive success, so nonbeneficial genetic traits will be more likely to remain in the gene pool. Biological anthropologist Jay T. Stock (2008) views environmental stress as needing to defeat two layers of protection before affecting our genetics. The first layer is our cultural adaptations. Our technology and knowledge can reduce pressure on one’s genotype to be “just right” to pass to the next generation. The second defense is our flexible physiology, such as our acclimatory responses. Only stressors not handled by these powerful responses would then cause natural selection on our alleles. These shields are already substantial, and cultural adaptations will only keep increasing in strength.
The increasing ability to travel far from one’s home region means that there will be a mixing of genetic variation on a global level in the future of our species. In recent centuries, gene flow of people around the world has increased, creating admixture in populations that had been separated for tens of thousands of years. For skin color, this means that populations all around the world could exhibit the whole range of skin colors, rather than the current pattern of decreasing melanin pigment farther from the equator. The same trend of intermixing would apply to all other traits, such as blood types. While our genetics will become more varied, the variation will be more intermixed instead of regionally isolated.
Our distant descendants will not likely be dextrous ultraintellectuals; more likely, they will be a highly variable and mobile species supported by novel cultural adaptations that make up for any inherited biological limitations. Technology may even enable the editing of DNA directly, changing these trends. With the uncertainty of our future, these are just the best-educated guesses for now. Our future is open and will be shaped little by little by the environment, our actions, and the actions of our descendants.
Summary
Modern Homo sapiens is the species that took the hominin lifestyle the furthest to become the only living member of that lineage. The largest factor that allowed us to persist while other hominins went extinct was likely our advanced ability to culturally adapt to a wide variety of environments. Our species, with its skeletal and behavioral traits, was well-suited to be generalist-specialists who successfully foraged across most of the world’s environments. The biological basis of this adaptation was our reorganized brain that facilitated innovation in cultural adaptations and intelligence for leveraging our social ties and finding ways to acquire resources from the environment. As the brain’s ability increased, it shaped the skull by reducing the evolutionary pressure to have large teeth and robust cranial bones to produce the modern Homo sapiens face.
Our ability to be generalist-specialists is seen in the geographical range that modern Homo sapiens covered in 300,000 years. In Africa, our species formed from multiregional gene flow that loosely connected archaic humans across the continent. People then expanded out to the rest of the continental Eurasia and even further to the Americas.
For most of our species’s existence, foraging was the general subsistence strategy within which people specialized to culturally adapt to their local environment. With omnivorousness and mobility, people found ways to extract and process resources, shaping the environment in return. When resource uncertainty hit the species, people around the world focused on agriculture to have a firmer control of sustenance. The new strategy shifted human history toward exponential growth and innovation, leading to our high dependence on cultural adaptations today.
While a cohesive image of our species has formed in recent years, there is still much to learn about our past. The work of many driven researchers shows that there are amazing new discoveries made all the time that refine our knowledge of human evolution. Technological innovations such as DNA analysis enable scientists to approach lingering questions from new angles. The answers we get allow us to ask even more insightful questions that will lead us to the next revelation. Like the pink limestone strata at Jebel Irhoud, previous effort has taken us so far and you are now ready to see what the next layer of discovery holds.
Hominin Species Summary
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Hominin |
Modern Homo sapiens |
|
Dates |
315,000 years ago to present |
|
Region(s) |
Starting in Africa, then expanding around the world |
|
Famous discoveries |
Cro-Magnon individuals, discovered 1868 in Dordogne, France. Otzi the Ice Man, discovered 1991 in the Alps between Austria and Italy. Kennewick man, discovered 1996 in Washington state. |
|
Brain size |
1400 cc average |
|
Dentition |
Extremely small with short cusps. |
|
Cranial features |
An extremely globular brain case and gracile features throughout the cranium. The mandibular symphysis forms a chin at the anterior-most point. |
|
Postcranial features |
Gracile skeleton adapted for efficient bipedal locomotion at the expense of the muscular strength of most other large primates. |
|
Culture |
Extremely extensive and varied culture with many spoken and written languages. Art is ubiquitous. Technology is broad in complexity and impact on the environment. |
|
Other |
The only living hominin. Chimpanzees and bonobos are the closest living relatives. |
Review Questions
- What are the skeletal and behavioral traits that define modern Homo sapiens? What are the evolutionary explanations for its presence?
- What are some creative ways that researchers have learned about the past by studying fossils and artifacts?
- How do the discoveries mentioned in “First Africa, Then the World” fit the Assimilation model?
- What is foraging? What adaptations do we have for this subsistence strategy? Could you train to be a skilled forager?
- What are aspects of your life that come from dependence on agriculture and its cultural effects? Where did the ingredients of your favorite foods originate from?
Key Terms
African multiregionalism: The idea that modern Homo sapiens evolved as a complex web of small regional populations with sporadic gene flow among them.
Agriculture: The mass production of resources through farming and domestication.
Aquaculture: The farming of fish using techniques such as trapping, channels, and artificial ponds.
Assimilation hypothesis: Current theory of modern human origins stating that the species evolved first in Africa and interbred with archaic humans of Europe and Asia.
Atlatl: A handheld spear thrower that increased the force of thrown projectiles.
Band: A small group of people living together as foragers.
Beringia: Ancient landmass that connected Siberia and Alaska. The ancestors of Indigenous Americans would have crossed this area to reach the Americas.
Carrying capacity: The amount of organisms that an environment can reliably support.
Coastal Route model: Theory that the first Paleoindians crossed to the Americas by following the southern coast of Beringia.
Early Modern Homo sapiens, Early Anatomically Modern Human: Terms used to refer to transitional fossils between archaic and modern Homo sapiens that have a mosaic of traits. Humans like ourselves, who mostly lack archaic traits, are referred to as Late Modern Homo sapiens and simply Anatomically Modern Humans.
Egalitarian: Human organization without strict ranks. Foraging societies tend to be more egalitarian than those based on other subsistence strategies.
Foraging: Lifestyle consisting of frequent movement through the landscape and acquiring resources with minimal storage capacity.
Generalist-specialist niche: The ability to survive in a variety of environments by developing local expertise. Evolution toward this niche may have been what allowed modern Homo sapiens to expand past the geographical range of other human species.
Globalization: A recent increase in the interconnectedness and interdependence of people that is facilitated with long-distance networks.
Globular: Having a rounded appearance. Increased globularity of the braincase is a trait of modern Homo sapiens.
Gracile: Having a smooth and slender quality; the opposite of robust.
Holocene: The epoch of the Cenozoic Era starting around 12,000 years ago and lasting arguably through the present.
Ice-Free Corridor model: Theory that the first Native Americans crossed to the Americas through a passage between glaciers.
Institutions: Long-lasting and influential cultural constructs. Examples include government, organized religion, academia, and the economy.
Last Glacial Maximum: The time 23,000 years ago when the most recent ice age was the most intense.
Later Stone Age: Time period following the Middle Stone Age with a diversification in tool types, starting around 50,000 years ago.
Levant: The eastern coast of the Mediterranean. The site of early modern human expansion from Africa and later one of the centers of agriculture.
Megafauna: Large ancient animals that may have been hunted to extinction by people around the world.
Mental eminence: The chin on the mandible of modern H. sapiens. One of the defining traits of our species.
Microlith: Small stone tool found in the Later Stone Age; also called a bladelet.
Middle Stone Age: Time period known for Mousterian lithics that connects African archaic to modern Homo sapiens.
Monumental architecture: Large and labor-intensive constructions that signify the power of the elite in a sedentary society. A common type is the pyramid, a raised crafted structure topped with a point or platform.
Mosaic: Composed from a mix or composite of traits.
Neolithic Revolution: Time of rapid change to human cultures due to the invention of agriculture, starting around 12,000 years ago.
Ochre: Iron-based mineral pigment that can be a variety of yellows, reds, and browns. Used by modern human cultures worldwide since at least 80,000 years ago.
Sahul: Ancient landmass connecting New Guinea and Australia.
Sedentarism: Lifestyle based on having a stable home area; the opposite of nomadism.
Southern Dispersal model: Theory that modern H. sapiens expanded from East Africa by crossing the Red Sea and following the coast east across Asia.
Subsistence strategy: The method an organism uses to find nourishment and other resources.
Sunda: Ancient Asian landmass that incorporated modern Southeast Asia.
Supraorbital torus: The bony brow ridge across the top of the eye orbits on many hominin crania.
Upper Paleolithic: Time period considered synonymous with the Later Stone Age.
Urbanization: The increase of population density as people settled together in cities.
Wallacea: Archipelago southeast of Sunda with different biodiversity than Asia.
Younger Dryas: The rapid change in global climate—notably a cooling of the Northern Hemisphere—13,000 years ago.
For Further Exploration
Websites
First-person virtual tour of Lascaux cave with annotated cave art: Ministère de la Culture and Musée d’Archéologie Nationale. “Visit the cave” Lascaux website.
Online anthropology magazine articles related to paleoanthropology and human evolution: SAPIENS. “Evolution.” SAPIENS website.
Various presentations of information about hominin evolution: Smithsonian Institution. “What does it mean to be human?” Smithsonian National Museum of Natural History website.
Magazine-style articles on archaeology and paleoanthropology: ThoughtCo. “Archaeology.” ThoughtCo. Website.
Database of comparisons across hominins and primates: University of California, San Diego. “MOCA Domains.” Center for Academic Research & Training in Anthropogeny website.
Books
Engaging book that covers human-made changes to the environment with industrialization and globalization: Kolbert, Elizabeth. 2014. The Sixth Extinction: An Unnatural History. New York: Bloomsbury.
Overview of what human life was like among the environmental shifts of the Ice Age: Woodward, Jamie. 2014. The Ice Age: A Very Short Introduction. Oxford: OUP Press.
Articles
Recent review paper about the current state of paleoanthropology research: Stringer, C. 2016. “The Origin and Evolution of Homo sapiens.” Philosophical Transactions of the Royal Society B 371 (1698).
Overview of the history of American paleoanthropology and the many debates that have occurred over the years: Trinkaus, E. 2018. “One Hundred Years of Paleoanthropology: An American Perspective.” American Journal of Physical Anthropology 165 (4): 638–651.
Amazing magazine article that synthesizes hominin evolution and why it is important to study this subject: Wheelwright, Jeff. 2015. “Days of Dysevolution.” Discover 36 (4): 33–39.
Fascinating research on Ötzi, a mummy from 5,000 years ago: Wierer, Ursula, Simona Arrighi, Stefano Bertola, Günther Kaufmann, Benno Baumgarten, Annaluisa Pedrotti, Patrizia Pernter, and Jacques Pelegrin. 2018. “The Iceman’s Lithic Toolkit: Raw Material, Technology, Typology and Use.” PLOS One 13 (6): e0198292. https://doi.org/10.1371/journal.pone.0198292.
Documentaries
PBS NOVA series covering the expansion of modern Homo sapiens and interbreeding with archaic humans: Brown, Nicholas, dir. 2015. First Peoples. Edmonton: Wall to Wall Television. Amazon Prime Video.
PBS NOVA special featuring the footprints found in White Sands National Park: Falk, Bella, dir. 2016. Ice Age Footprints. Boston: Windfall Films. https://www.pbs.org/wgbh/nova/video/ice-age-footprints/.
PBS NOVA special about how modern humans evolved adaptations to different environments. Shows how present-day people live around the world: Thompson, Niobe, dir. 2016. Great Human Odyssey. Edmonton: Clearwater Documentary. https://www.pbs.org/wgbh/nova/evolution/great-human-odyssey.html.
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Acknowledgments
I could not have undertaken this project without the help of many who got me to where I am today. I extend sincere thank yous to the many colleagues and former students who have inspired me to keep learning and talking about anthropology. Thank you also to all who are involved in this textbook project. The anonymous reviewers truly sparked improvements to the chapter. Lastly, the staff of Starbucks #5772 also contributed immensely to this text.
Keith Chan, Ph.D., Grossmont-Cuyamaca Community College District and MiraCosta College
This chapter is a revision from "Chapter 12: Modern Homo sapiens” by Keith Chan. In Explorations: An Open Invitation to Biological Anthropology, first edition, edited by Beth Shook, Katie Nelson, Kelsie Aguilera, and Lara Braff, which is licensed under CC BY-NC 4.0.
Learning Objectives
- Identify the skeletal and behavioral traits that represent modern Homo sapiens.
- Critically evaluate different types of evidence for the origin of our species in Africa and our expansion around the world.
- Understand how the human lifestyle changed when people transitioned from foraging to agriculture.
- Hypothesize how human evolutionary trends may continue into the future.
The walls of a pink limestone cave in the hillside of Jebel Irhoud jutted out of the otherwise barren landscape of the Moroccan desert (Figure 13.1). Miners had excavated the cave in the 1960s, revealing some fossils. In 2007, a re-excavation of the site became a momentous occasion for science. A fossil cranium unearthed by a team of researchers was barely visible to the untrained eye. Just the fossil’s robust brows were peering out of the rock. This research team from the Max Planck Institute for Evolutionary Anthropology was the latest to explore the ancient human presence in this part of North Africa after a find by miners in 1960. Excavating near the first discovery, the researchers wanted to learn more about how Homo sapiens lived far from East Africa, where we thought our species originated.
The scientists were surprised when they analyzed the cranium, named Irhoud 10, and other fossils. Statistical comparisons with other human crania concluded that the Irhoud face shapes were typical of recent modern humans while the braincases matched ancient modern humans. Based on the findings of other scientists, the team expected these modern Homo sapiens fossils to be around 200,000 years old. Instead, dating revealed that the cranium had been buried for around 315,000 years.
Together, the modern-looking facial dimensions and the older date reshaped the interpretation of our species: modern Homo sapiens. Some key evolutionary changes from the archaic Homo sapiens (described in Chapter 11) to our species today happened 100,000 years earlier than we had thought and across the vast African continent rather than concentrated in its eastern region.
This revelation in the study of modern Homo sapiens is just one of the latest in this continually advancing area of biological anthropology. Researchers today are still discovering amazing fossils and ingenious ways to collect data and test hypotheses about our past. Through the collective work of many scientists, we are building an overall theory of modern human origins.
Defining Modernity
What defines modern Homo sapiens when compared to archaic Homo sapiens? Modern humans, like you and me, have a set of derived traits that are not seen in archaic humans or any other hominin. As with other transitions in hominin evolution, such as increasing brain size and bipedal ability, modern traits do not appear fully formed or all at once. In other words, the first modern Homo sapiens was not just born one day from archaic parents. The traits common to modern Homo sapiens appeared in a mosaic manner: gradually and out of sync with one another. There are two areas to consider when tracking the complex evolution of modern human traits. One is the physical change in the skeleton. The other is behavior inferred from the size and shape of the cranium and material culture evidence.
Skeletal Traits
The skeleton of modern Homo sapiens is less robust than that of archaic Homo sapiens. In other words, the modern skeleton is gracile, meaning that the structures are thinner and smoother. Differences related to gracility in the cranium are seen in the braincase, the face, and the mandible. There are also broad differences in the rest of the skeleton.
Cranial Traits
Several elements of the braincase differ between modern and archaic Homo sapiens. Overall, the shape is much rounder, or more globular, on a modern skull (Lieberman, McBratney, and Krovitz 2002; Neubauer, Hublin, and Gunz 2018; Pearson 2008; Figure 13.2). You can feel the globularity of your own modern human skull. Feel the height of your forehead with the palm of your hand. Viewed from the side, the tall vertical forehead of a modern Homo sapiens stands out when compared to the sloping archaic version. This is because the frontal lobe of the modern human brain is larger than the one in archaic humans, and the skull has to accommodate the expansion. The vertical forehead reduces a trait that is common to all other hominins: the brow ridge or supraorbital torus. The parietal lobes of the brain and the matching parietal bones on either side of the skull both bulge outward more in modern humans. At the back of the skull, the archaic occipital bun is no longer present. Instead, the occipital region of the modern human cranium has a derived tall and smooth curve, again reflecting the globular brain inside.
The trend of shrinking face size across hominins reaches its extreme with our species as well. The facial bones of a modern Homo sapiens are extremely gracile compared to all other hominins (Lieberman, McBratney, and Krovitz 2002). Continuing a trend in hominin evolution, technological innovations kept reducing the importance of teeth in reproductive success (Lucas 2007). As natural selection favored smaller and smaller teeth, the surrounding bone holding these teeth also shrank.
Related to smaller teeth, the mandible is also gracile in modern humans when compared to archaic humans and other hominins. Interestingly, our mandibles have pulled back so far from the prognathism of earlier hominins that we gained an extra structure at the most anterior point, called the mental eminence. You know this structure as the chin. At the skeletal level, it resembles an upside-down “T” at the centerline of the mandible (Pearson 2008). Looking back at archaic humans, you will see that they all lack a chin. Instead, their mandibles curve straight back without a forward point. What is the chin for and how did it develop? Flora Gröning and colleagues (2011) found evidence of the chin’s importance by simulating physical forces on computer models of different mandible shapes. Their results showed that the chin acts as structural support to withstand strain on the otherwise gracile mandible.
Postcranial Gracility
The rest of the modern human skeleton is also more gracile than its archaic counterpart. The differences are clear when comparing a modern Homo sapiens with a cold-adapted Neanderthal (Sawyer and Maley 2005), but the trends are still present when comparing modern and archaic humans within Africa (Pearson 2000). Overall, a modern Homo sapiens postcranial skeleton has thinner cortical bone, smoother features, and more slender shapes when compared to archaic Homo sapiens (Figure 13.3). Comparing whole skeletons, modern humans have longer limb proportions relative to the length and width of the torso, giving us lankier outlines.
Why is our skeleton so gracile compared to those of other hominins? Natural selection can drive the gracilization of skeletons in several ways (Lieberman 2015). A slender frame is believed to be adapted for the efficient long-distance running ability that started with Homo erectus. Furthermore, it is argued that slenderness is a genetic adaptation for cooling an active body in hotter climates, which aligns with the ample evidence that Africa was the home continent of our species.
Behavioral Modernity
Aside from physical differences in the skeleton, researchers have also uncovered evidence of behavioral changes associated with increased cultural complexity from archaic to modern humans. How did cultural complexity develop? Two investigations into this question are archaeology and the analysis of reconstructed brains.
Archaeology tells us much about the behavioral complexity of past humans by interpreting the significance of material culture. In terms of advanced culture, items created with an artistic flair, or as decoration, speak of abstract thought processes (Figure 13.4). The demonstration of difficult artistic techniques and technological complexity hints at social learning and cooperation as well. According to paleoanthropologist John Shea (2011), one way to track the complexity of past behavior through artifacts is by measuring the variety of tools found together. The more types of tools constructed with different techniques and for different purposes, the more modern the behavior. Researchers are still working on an archaeological way to measure cultural complexity that is useful across time and place.
The interpretation of brain anatomy is another promising approach to studying the evolution of human behavior. When looking at investigations on this topic in modern Homo sapiens brains, researchers found a weak association between brain size and test-measured intelligence (Pietschnig et al. 2015). Additionally, they found no association between intelligence and biological sex. These findings mean that there are more significant factors that affect tested intelligence than just brain size. Since the sheer size of the brain is not useful for weighing intelligence within a species, paleoanthropologists are instead investigating the differences in certain brain structures. The differences in organization between modern Homo sapiens brains and archaic Homo sapiens brains may reflect different cognitive priorities that account for modern human culture. As with the archaeological approach, new discoveries will refine what we know about the human brain and apply that knowledge to studying the distant past.
Taken together, the cognitive abilities in modern humans may have translated into an adept use of tools to enhance survival. Researchers Patrick Roberts and Brian A. Stewart (2018) call this concept the generalist-specialist niche: our species is an expert at living in a wide array of environments, with populations culturally specializing in their own particular surroundings. The next section tracks how far around the world these skeletal and behavioral traits have taken us.
First Africa, Then the World
What enabled modern Homo sapiens to expand its range further in 300,000 years than Homo erectus did in 1.5 million years? The key is the set of derived biological traits from the last section. It is theorized that the gracile frame and neurological anatomy allowed modern humans to survive and even flourish in the vastly different environments they encountered. Based on multiple types of evidence, the source of all of these modern humans was Africa. Instead of originating from just one location, evidence shows that modern Homo sapiens evolution occurred in a complex gene flow network across Africa, a concept called African multiregionalism (Scerri et al. 2018).
This section traces the origin of modern Homo sapiens and the massive expansion of our species across all of the continents (except Antarctica) by 12,000 years ago. While modern Homo sapiens first shared geography with archaic humans, modern humans eventually spread into lands where no human had gone before. Figure 13.5 shows the broad routes that our species took expanding around the world. I encourage you to make your own timeline with the dates in this part to see the overall trends.
Modern Homo sapiens Biology and Culture in Africa
We start with the ample fossil evidence supporting the theory that modern humans originated in Africa during the Middle Pleistocene, having evolved from African archaic Homo sapiens. The earliest dated fossils considered to be modern actually have a mosaic of archaic and modern traits, showing the complex changes from one type to the other. Experts have various names for these transitional fossils, such as Early Modern Homo sapiens or Early Anatomically Modern Humans. However they are labeled, the presence of some modern traits means that they illustrate the origin of the modern type. Three particularly informative sites with fossils of the earliest modern Homo sapiens are Jebel Irhoud, Omo, and Herto.
Recall from the start of the chapter that the most recent finds at Jebel Irhoud are now the oldest dated fossils that exhibit some facial traits of modern Homo sapiens. Besides Irhoud 10, the cranium that was dated to 315,000 years ago (Hublin et al. 2017; Richter et al. 2017), there were other fossils found in the same deposit that we now know are from the same time period. In total there are at least five individuals, representing life stages from childhood to adulthood. These fossils form an image of high variation in skeletal traits. For example, the skull named Irhoud 1 has a primitive brow ridge, while Irhoud 2 and Irhoud 10 do not (Figure 13.6). The braincases are lower than what is seen in the modern humans of today but higher than in archaic Homo sapiens. The teeth also have a mix of archaic and modern traits that defy clear categorization into either group.
Research separated by nearly four decades uncovered fossils and artifacts from the Kibish Formation in the Lower Omo Valley in Ethiopia. These Omo Kibish hominins were represented by braincases and fragmented postcranial bones of three individuals found kilometers apart, dating back to around 233,000 years ago (Day 1969; McDougall, Brown, and Fleagle 2005; Vidal et al. 2022). One interesting finding was the variation in braincase size between the two more-complete specimens: while the individual named Omo I had a more globular dome, Omo II had an archaic-style long and low cranium.
Also in Ethiopia, a team led by Tim White (2003) excavated numerous fossils at Herto. There were fossilized crania of two adults and a child, along with fragments of more individuals. The dates ranged between 160,000 and 154,000 years ago. The skeletal traits and stone-tool assemblage were both intermediate between the archaic and modern types. Features reminiscent of modern humans included a tall braincase and thinner zygomatic (cheek) bones than those of archaic humans (Figure 13.7). Still, some archaic traits persisted in the Herto fossils, such as the supraorbital tori. Statistical analysis by other research teams concluded that at least some cranial measurements fit just within the modern human range (McCarthy and Lucas 2014), favoring categorization with our own species.
The timeline of material culture suggests a long period of relying on similar tools before a noticeable diversification of artifacts types. Researchers label the time of stable technology shared with archaic types the Middle Stone Age, while the subsequent time of diversification in material culture is called the Later Stone Age.
In the Middle Stone Age, the sites of Jebel Irhoud, Omo, and Herto all bore tools of the same flaked style as archaic assemblages, even though they were separated by almost 150,000 years. The consistency in technology may be evidence that behavioral modernity was not so developed. No clear signs of art dating back this far have been found either. Other hypotheses not related to behavioral modernity could explain these observations. The tool set may have been suitable for thriving in Africa without further innovation. Maybe works of art from that time were made with media that deteriorated or perhaps such art was removed by later humans.
Evidence of what Homo sapiens did in Africa from the end of the Middle Stone Age to the Later Stone Age is concentrated in South African cave sites that reveal the complexity of human behavior at the time. For example, Blombos Cave, located along the present shore of the Cape of Africa facing the Indian Ocean, is notable for having a wide variety of artifacts. The material culture shows that toolmaking and artistry were more complex than previously thought for the Middle Stone Age. In a layer dated to 100,000 years ago, researchers found two intact ochre-processing kits made of abalone shells and grinding stones (Henshilwood et al. 2011). Marine snail shell beads from 75,000 years ago were also excavated (Figure 13.8; d’Errico et al. 2005). Together, the evidence shows that the Middle Stone Age occupation at Blombos Cave incorporated resources from a variety of local environments into their culture, from caves (ochre), open land (animal bones and fat), and the sea (abalone and snail shells). This complexity shows a deep knowledge of the region’s resources and their use—not just for survival but also for symbolic purposes.
On the eastern coast of South Africa, Border Cave shows new African cultural developments at the start of the Later Stone Age. Paola Villa and colleagues (2012) identified several changes in technology around 43,000 years ago. Stone-tool production transitioned from a slower process to one that was faster and made many microliths, small and precise stone tools. Changes in decorations were also found across the Later Stone Age transition. Beads were made from a new resource: fragments of ostrich eggs shaped into circular forms resembling present-day breakfast cereal O’s (d’Errico et al. 2012). These beads show a higher level of altering one’s own surroundings and a move from the natural to the abstract in terms of design.
Expansion into the Middle East and Asia
While modern Homo sapiens lived across Africa, some members eventually left the continent. These pioneers could have used two connections to the Middle East or West Asia. From North Africa, they could have crossed the Sinai Peninsula and moved north to the Levant, or eastern Mediterranean. Finds in that region show an early modern human presence. Other finds support the Southern Dispersal model, with a crossing from East Africa to the southern Arabian Peninsula through the Straits of Bab-el-Mandeb. It is tempting to think of one momentous event in which people stepped off Africa and into the Middle East, never to look back. In reality, there were likely multiple waves of movement producing gene flow back and forth across these regions as the overall range pushed east. The expanding modern human population could have thrived by using resources along the southern coast of the Arabian Peninsula to South Asia, with side routes moving north along rivers. The maximum range of the species then grew across Asia.
Modern Homo sapiens in the Middle East
Geographically, the Middle East is the ideal place for the African modern Homo sapiens population to inhabit upon expanding out of their home continent. In the Eastern Mediterranean coast of the Levant, there is a wealth of skeletal and material culture linked to modern Homo sapiens. Recent discoveries from Saudi Arabia further add to our view of human life just beyond Africa.
The Caves of Mount Carmel in present-day Israel have preserved skeletal remains and artifacts of modern Homo sapiens, the first-known group living outside Africa. The skeletal presence at Misliya Cave is represented by just part of the left upper jaw of one individual, but it is notable for being dated to a very early time, between 194,000 and 177,000 years ago (Hershkovitz et al. 2018). Later, from 120,000 to 90,000 years ago, fossils of multiple individuals across life stages were found in the caves of Es-Skhul and Qafzeh (Shea and Bar-Yosef 2005). The skeletons had many modern Homo sapiens traits, such as globular crania and more gracile postcranial bones when compared to Neanderthals. Still, there were some archaic traits. For example, the adult male Skhul V also possessed what researchers Daniel Lieberman, Osbjorn Pearson, and Kenneth Mowbray (2000) called marked or clear occipital bunning. Also, compared to later modern humans, the Mount Carmel people were more robust. Skhul V had a particularly impressive brow ridge that was short in height but sharply jutted forward above the eyes (Figure 13.9). The high level of preservation is due to the intentional burial of some of these people. Besides skeletal material, there are signs of artistic or symbolic behavior. For example, the adult male Skhul V had a boar’s jaw on his chest. Similarly, Qafzeh 11, a juvenile with healed cranial trauma, had an impressive deer antler rack placed over his torso (Figure 13.10; Coqueugniot et al. 2014). Perforated seashells colored with ochre, mineral-based pigment, were also found in Qafzeh (Bar-Yosef Mayer, Vandermeersch, and Bar-Yosef 2009).
One remaining question is, what happened to the modern humans of the Levant after 90,000 years ago? Another site attributed to our species did not appear in the region until 47,000 years ago. Competition with Neanderthals may have accounted for the disappearance of modern human occupation since the Neanderthal presence in the Levant lasted longer than the dates of the early modern Homo sapiens. John Shea and Ofer Bar-Yosef (2005) hypothesized that the Mount Carmel modern humans were an initial expansion from Africa that failed. Perhaps they could not succeed due to competition with the Neanderthals who had been there longer and had both cultural and biological adaptations to that environment.
Modern Homo sapiens of China
A long history of paleoanthropology in China has found ample evidence of modern human presence. Four notable sites are the caves at Fuyan, Liujiang, Tianyuan, and Zhoukoudian. In the distant past, these caves would have been at least seasonal shelters that unintentionally preserved evidence of human presence for modern researchers to discover.
At Fuyan Cave in Southern China, paleoanthropologists found 47 adult teeth associated with cave formations dated to between 120,000 and 80,000 years ago (Liu et al. 2015). It is currently the oldest-known modern human site in China, though other researchers question the validity of the date range (Michel et al. 2016). The teeth have the small size and gracile features of modern Homo sapiens dentition.
The fossil Liujiang (or Liukiang) hominin (67,000 years ago) has derived traits that classified it as a modern Homo sapiens, though primitive archaic traits were also present. In the skull, which was found nearly complete, the Liujiang hominin had a taller forehead than archaic Homo sapiens but also had an enlarged occipital region (Figure 13.11; Brown 1999; Wu et al. 2008). Other parts of the skeleton also had a mix of modern and archaic traits: for example, the femur fragments suggested a slender length but with thick bone walls (Woo 1959).
Another Chinese site to describe here is the one that has been studied the longest. In the Zhoukoudian Cave system (Figure 13.12), where Homo erectus and archaic Homo sapiens have also been found, there were three crania of modern Homo sapiens. These crania, which date to between 34,000 and 10,000 years ago, were all more globular than those of archaic humans but still lower and longer than those of later modern humans (Brown 1999; Harvati 2009). When compared to one another, the crania showed significant differences from one another. Comparison of cranial measurements to other populations past and present found no connection with modern East Asians, again showing that human variation was very different from what we see today.
Crossing to Australia
Expansion of the first modern human Asians, still following the coast, eventually entered an area that researchers call Sunda before continuing on to modern Australia. Sunda was a landmass made up of the modern-day Malay Peninsula, Sumatra, Java, and Borneo. Lowered sea levels connected these places with land bridges, making them easier to traverse. Proceeding past Sunda meant navigating Wallacea, the archipelago that includes the Indonesian islands east of Borneo. In the distant past, there were many megafauna, large animals that migrating humans would have used for food and materials (such as utilizing animals’ hides and bones). Further southeast was another landmass called Sahul, which included New Guinea and Australia as one contiguous continent. Based on fossil evidence, this land had never seen hominins or any other primates before modern Homo sapiens arrived. Sites along this path offer clues about how our species handled the new environment to live successfully as foragers.
The skeletal remains at Lake Mungo, land traditionally owned by Mutthi Mutthi, Ngiampaa, and Paakantji peoples, are the oldest known in the continent. The now-dry lake was one of a series located along the southern coast of Australia in New South Wales, far from where the first people entered from the north (Barbetti and Allen 1972; Bowler et al. 1970). Two individuals dating to around 40,000 years ago show signs of artistic and symbolic behavior, including intentional burial. The bones of Lake Mungo 1 (LM1), an adult female, were crushed repeatedly, colored with red ochre, and cremated (Bowler et al. 1970). Lake Mungo 3 (LM3), a tall, older male with a gracile cranium but robust postcranial bones, had his fingers interlocked over his pelvic region (Brown 2000).
Kow Swamp, within traditional Yorta Yorta land also in southern Australia, contained human crania that looked distinctly different from the ones at Lake Mungo (Durband 2014; Thorne and Macumber 1972). The crania, dated between 9,000 and 20,000 years ago, had extremely robust brow ridges and thick bone walls, but these were paired with globular features on the braincase (Figure 13.13).
While no fossil humans have been found at the Madjedbebe rock shelter in the North Territory of Australia, more than 10,000 artifacts found there show both behavioral modernity and variability (Clarkson et al. 2017). They include a diverse array of stone tools and different shades of ochre for rock art, including mica-based reflective pigment (similar to glitter). These impressive artifacts are as far back as 56,000 years old, providing the date for the earliest-known presence of humans in Australia.
From the Levant to Europe
The first modern human expansion into Europe occurred after other members of our species settled in East Asia and Australia. As the evidence from the Levant suggests, modern human movement to Europe may have been hampered by the presence of Neanderthals. It is suggested that another obstacle was the colder climate, which was incompatible with the biology of modern Homo sapiens from Africa, as they were adapted to high temperatures and ultraviolet radiation. Still, by 40,000 years ago, modern Homo sapiens had a detectable presence. This time was also the start of the Later Stone Age or Upper Paleolithic, when there was an expansion in cultural complexity. There is a wealth of evidence from this region due to a Western bias in research, the proximity of these findings to Western scientific institutions, and the desire of Western scientists to explore their own past.
In Romania, the site of Peștera cu Oase (Cave of Bones) had the oldest-known remains of modern Homo sapiens in Europe, dated to around 40,000 years ago (Trinkaus et al. 2003a). Among the bones and teeth of many animals were the fragmented cranium of one person and the mandible of another (the two bones did not fit each other). Both bones have modern human traits similar to the fossils from the Middle East, but they also had Neanderthal traits. Oase 1, the mandible, had a mental eminence but also extremely large molars (Trinkaus et al. 2003b). This mandible has yielded DNA that surprisingly is equally similar to DNA from present-day Europeans and Asians (Fu et al. 2015). This means that Oase 1 was not the direct ancestor of modern Europeans. The Oase 2 cranium has the derived traits of reduced brow ridges along with archaic wide zygomatic cheekbones and an occipital bun (Figure 13.14; Rougier et al. 2007).
Dating to around 26,000 years ago, Předmostí near Přerov in the Czech Republic was a site where people buried over 30 individuals along with many artifacts. Eighteen individuals were found in one mass burial area, a few covered by the scapulae of woolly mammoths (Germonpré, Lázničková-Galetová, and Sablin 2012). The Předmostí crania were more globular than those of archaic humans but tended to be longer and lower than in later modern humans (Figure 13.15; Velemínská et al. 2008). The height of the face was in line with modern residents of Central Europe. There was also skeletal evidence of dog domestication, such as the presence of dog skulls with shorter snouts than in wild wolves (Germonpré, Lázničková-Galetová, and Sablin et al. 2012). In total, Předmostí could have been a settlement dependent on mammoths for subsistence and the artificial selection of early domesticated dogs.
The sequence of modern Homo sapiens technological change in the Later Stone Age has been thoroughly dated and labeled by researchers working in Europe. Among them, the Gravettian tradition of 33,000 years to 21,000 years ago is associated with most of the known curvy female figurines, often assumed to be “Venus” figures. Hunting technology also advanced in this time with the first known boomerang, atlatl (spear thrower), and archery. The Magdalenian tradition spread from 17,000 to 12,000 years ago. This culture further expanded on fine bone tool work, including barbed spearheads and fishhooks (Figure 13.16).
Among the many European sites dating to the Later Stone Age, the famous cave art sites deserve mention. Chauvet-Pont-d'Arc Cave in southern France dates to separate Aurignacian occupations 31,000 years ago and 26,000 years ago. Over a hundred art pieces representing 13 animal species are preserved, from commonly depicted deer and horses to rarer rhinos and owls. Another French cave with art is Lascaux, which is several thousand years younger at 17,000 years ago in the Magdalenian period. At this site, there are over 6,000 painted figures on the walls and ceiling (Figure 13.17). Scaffolding and lighting must have been used to make the paintings on the walls and ceiling deep in the cave. Overall, visiting Lascaux as a contemporary must have been an awesome experience: trekking deeper in the cave lit only by torches giving glimpses of animals all around as mysterious sounds echoed through the galleries.
Special Topic: Cannibalism and Culture - Mortuary Practices in Modern Homo sapiens.
Within a 2017 publication in the Journal of Archaeological Method and Theory, Saladié and Rodríguez-Hidalgo bring light to traces of early cannibalism in western Eurasia, arguing that context-specific cannibalistic practices were present throughout the Pleistocene and increased notably from the end of the Upper Palaeolithic and onward (Saladié & Rodriguez-Hidalgo, 2017). While early hominins and Neandertals are recognized in this research, the authors highlight the presence of these mortuary practices in a cluster of Homo Sapien sites. More recent research uncovers similar findings that back these claims as well, where human bones in Herto Ethiopia, Maszycka Cave Poland, and Gough’s Cave in the United Kingdom show anthropogenic defleshing and other modifications which have been interpreted as cannibalism (Pobiner, Et al. 2023). These findings suggest that cannibalistic behaviours formed a recurring aspect of modern human behaviour in certain ecological and cultural contexts.
A significant example comes from the Neolithic levels of Fontbrégua Cave in southeastern France, where Paola Villa and colleagues compared clusters of human bones with the remains of wild and domestic animals from the same sediments. The study found that human bodies were butchered, processed, and most likely eaten in a way that parallels animal carcass treatment, including the placement and timing of cut marks, dismemberment sequences, and perimortem fractures to open marrow cavities (Villa, Et al. 1986). As the assemblage comes from a primary depositional context with pristine preservation and careful excavation, the authors suggest that cannibalism is the only satisfactory explanation for the pattern of cut marks and breakage seen on the human bones.
More recent work has furthered this hypothesis for Late Upper Palaeolithic Homo sapiens, especially in Magdalenian contexts. In a 2023 study, researchers combined archeological and genetic evidence from fifty-nine Magdalenian sites, concluding that this specific culture shows an unusually high frequency of cannibalistic cases compared to earlier and later hominin groups; so much so that they identify “primary burial and cannibalism” as the two main mortuary expressions (Marsh & Bello, 2023). Additionally, new analyses from Maszycka Cave in Poland have described cut and broken human bones in patterns consistent with human consumption, reinforcing this cannibalism hypothesis (Marginedas & Saladié, 2025). Together, these studies suggest that for some Magdalenian groups, mortuary cannibalism was a habitual way of disposing of the dead, not just a one-off crisis response. At the same time, researchers emphasize that not every modified skeleton indicates blatant consumption of the dead and that ritual or symbolic perspectives must also be considered. Previously noted in chapter eleven, Ullrich’s survey of European mortuary practices presents frequent manipulations of corpses from the Palaeolithic through the Hallstatt period. Said manipulations include cut marks, dismemberment, skull fracturing, and marrow extraction (Ullrich, 2005, p. 258), which Ullrich interprets as cannibalistic rites embedded in cult ceremonies rather than everyday subsistence. In the author’s view, some Palaeolithic groups may have believed that consuming members of their community allowed them to take on the strengths, abilities, or even mental aspects of their dead member; the act of cannibalism may have functioned as a form of appropriating physical and mental powers rather than simply obtaining calories. With that, Neolithic assemblages show how careful taphonomic work can distinguish cuts linked to interpersonal violence from those associated with systemic butchery (Marginedas & Saladié, 2025). The findings seek to highlight that some Homo sapiens populations combined ritual, mortuary, and nutritional motives when processing human remains.
These past and contemporary findings are significant for future anthropology students as they shed light on biological anthropology methodology and interpretation. Archaeologists are able to distinguish between occasions when humans were handled like any other carcass and times when they were handled in more symbolic ways thanks to factors like cut mark orientation, the timing of bone breakage, and direct comparison with animal remains. Readers interested in exploring this topic further should investigate the context-specific motivations for cannibalism, like nutritional stress, warfare, funerary sites, or ritual power appropriation.
Similar archeological techniques have been used to explore behaviours of cannibalism among Indigenous Huron-Wendat populations in 1651 Canada, where human bones exhibit cutmarks, perimortem fractures, and thermal modifications (Spence & Jackson, 2014). These shared taphonomic signatures across continents reveal recurring practices under ecological stress, bridging prehistoric Europe to North American contexts. Engaging with such analytical techniques opens up new ways that archeologists and anthropologists can investigate the variability in human behaviour, from nutritional crises to mortuary rituals.
Peopling of the Americas
By 25,000 years ago, our species was the only member of Homo left on Earth. Gone were the Neanderthals, Denisovans, Homo naledi, and Homo floresiensis. The range of modern Homo sapiens kept expanding eastward into—using the name given to this area by Europeans much later—the Western Hemisphere. This section will address what we know about the peopling of the Americas, from the first entry to these continents to the rapid spread of Indigenous Americans across its varied environments.
While evidence points to an ancient land bridge called Beringia that allowed people to cross from what is now northeastern Siberia into modern-day Alaska, what people did to cross this land bridge is still being investigated. For most of the 20th century, the accepted theory was the Ice-Free Corridor model. It stated that northeast Asians (East Asians and Siberians) first expanded across Beringia inland through a passage between glaciers that opened into the western Great Plains of the United States, just east of the Rocky Mountains, around 13,000 years ago (Swisher et al. 2013). While life up north in the cold environment would have been harsh, migrating birds and an emerging forest might have provided sustenance as generations expanded through this land (Potter et al. 2018).
However, in recent decades, researchers have accumulated evidence against the Ice-Free Corridor model. Archaeologist K. R. Fladmark (1979) brought the alternate Coastal Route model into the archaeological spotlight; researcher Jon M. Erlandson has been at the forefront of compiling support for this theory (Erlandson et al. 2015). The new focus is the southern edge of the land bridge instead of its center: About 16,000 years ago, members of our species expanded along the coastline from northeast Asia, east through Beringia, and south down the Pacific Coast of North America while the inland was still sealed off by ice. The coast would have been free of ice at least part of the year, and many resources would have been found there, such as fish (e.g., salmon), mammals (e.g., whales, seals, and otters), and plants (e.g., seaweed).
South through the Americas
When the first modern Homo sapiens reached the Western Hemisphere, the spread through the Americas was rapid. Multiple migration waves crossed from North to South America (Posth et al. 2018). Our species took advantage of the lack of hominin competition and the bountiful resources both along the coasts and inland. The Americas had their own wide array of megafauna, which included woolly mammoths (Figure 13.18), mastodons, camels, horses, ground sloths, giant tortoises, and—a favorite of researchers—a two-meter-tall beaver. The reason we cannot see these amazing animals today may be that resources gained from these fauna were crucial to the survival for people over 12,000 years ago (Araujo et al. 2017). Several sites are notable for what they add to our understanding of the distant past in the Americas, including interactions with megafauna and other elements of the environment.
A 2019 discovery may allow researchers to improve theories about the peopling of the Americas. In White Sands National Park, New Mexico, 60 human footprints have been astonishingly dated to around 22,000 years ago (Bennett et al. 2021). This date and location do not match either the Ice-Free Corridor or Coastal Route models. Researchers are now working to verify the find and adjust previous models to account for the new evidence. This groundbreaking find is sparking new theories; it is another example of the fast pace of research performed on our past.
Monte Verde is a landmark site that shows that the human population had expanded down the whole vertical stretch of the Americas to Chile by 14,600 years ago. The site has been excavated by archaeologist Tom D. Dillehay and his team (2015). The remains of nine distinct edible species of seaweed at the site shows familiarity with coastal resources and relates to the Coastal Route model by showing a connection between the inland people and the sea.
Named after the town in New Mexico, the Clovis stone-tool style is the first example of a widespread culture across much of North America, between 13,400 and 12,700 years ago (Miller, Holliday, and Bright 2013). Clovis points were fluted with two small projections, one on each end of the base, facing away from the head (Figure 13.19). The stone points found at this site match those found as far as the Canadian border and northern Mexico, and from the west coast to the east coast of the United States. Fourteen Clovis sites also contained the remains of mammoths or mastodons, suggesting that hunting megafauna with these points was an important part of life for the Clovis people. After the spread of the Clovis style, it diversified into several regional styles, keeping some of the Clovis form but also developing their own unique touches.
The Big Picture: The Assimilation Hypothesis
How do researchers make sense of all of these modern Homo sapiens discoveries that cover over 300,000 years of time and stretch across every continent except Antarctica? How was modern Homo sapiens related to archaic Homo sapiens?
The Assimilation hypothesis proposes that modern Homo sapiens evolved in Africa first and expanded out but also interbred with the archaic Homo sapiens they encountered outside Africa (Figure 13.20). This hypothesis is powerful since it explains why Africa has the oldest modern human fossils, why early modern humans found in Europe and Asia bear a resemblance to the regional archaics, and why traces of archaic DNA can be found in our genomes today (Dannemann and Racimo 2018; Reich et al. 2010; Reich et al. 2011; Slatkin and Racimo 2016; Smith et al. 2017; Wall and Yoshihara Caldeira Brandt 2016).
While researchers have produced a model that satisfies the data, there are still a lot of questions for paleoanthropologists to answer regarding our origins. What were the patterns of migration in each part of the world? Why did the archaic humans go extinct? In what ways did archaic and modern humans interact? The definitive explanation of how our species started and what our ancestors did is still out there to be found. You are now in a great place to welcome the next discovery about our distant past—maybe you’ll even contribute to our understanding as well.
The Chain Reaction of Agriculture
While it may be hard to imagine today, for most of our species’ existence we were nomadic: moving through the landscape without a singular home. Instead of a refrigerator or pantry stocked with food, we procured nutrition and other resources as needed based on what was available in the environment. This section gives an overview of how the foraging lifestyle enabled the expansion of our species and how the invention of a new way of life caused a chain reaction of cultural change.
The Foraging Tradition
There are a variety of possible subsistence strategies, or methods of finding sustenance and resources. To understand our species is to understand the subsistence strategy of foraging, or the search for resources in the environment. While most (but not all) humans today live in cultures that practice agriculture (whereby we greatly shape the environment to mass produce what we need), we have spent far more time as nomadic foragers than as settled agriculturalists. As such, it has been suggested that our traits have evolved to be primarily geared toward foraging. For instance, our efficient bipedalism allows persistence-hunting across long distances as well as movement from resource to resource.
How does human foraging, also known as hunting and gathering, work? Anthropologists have used all four fields to answer this question (see Ember n.d.). Typically, people formed bands, or kin-based groups of around 50 people or less (rarely over 100). A band’s organization would be egalitarian, with a flexible hierarchy based on an individual’s age, level of experience, and relationship with others. Everyone would have a general knowledge of the skills assigned to their gender roles, rather than specializing in different occupations. A band would be able to move from place to place in the environment, using knowledge of the area to forage (Figure 13.21). In varied environments—from savannas to tropical forests, deserts, coasts, and the Arctic circle—people found sustenance needed for survival.
Humans made extensive use of the foraging subsistence strategy, but this lifestyle did have limitations. The ease of foraging depended on the richness of the environment. Due to the lack of storage, resources had to be dependably found when needed. While a bountiful environment would require just a few hours of foraging a day and could lead to a focus on one location, the level and duration of labor increased greatly in poor or unreliable environments. Labor was also needed to process the acquired resources, which contributed to the foragers’ daily schedule (Crittenden and Schnorr 2017).
The adaptations to foraging found in modern Homo sapiens may explain why our species became so successful both within Africa and in the rapid expansion around the world. Overcoming the limitations, each generation at the edge of our species’s range would have found it beneficial to expand a little further, keeping contact with other bands but moving into unexplored territory where resources were more plentiful. The cumulative effect would have been the spread of modern Homo sapiens across continents and hemispheres.
Why Agriculture?
After hundreds of thousands of years of foraging, some groups of people around 12,000 years ago started to practice agriculture. This transition, called the Neolithic Revolution, occurred at the start of the Holocene epoch. While the reasons for this global change are still being investigated, two likely co-occurring causes are a growing human population and natural global climate change.
Overcrowding could have affected the success of foraging in the environment, leading to the development of a more productive subsistence strategy (Cohen 1977). Foraging works best with low population densities since each band needs a lot of space to support itself. If too many people occupy the same environment, they deplete the area faster. The high population could exceed the carrying capacity, or number of people a location can reliably support. Reaching carrying capacity on a global level due to growing population and limited areas of expansion would have been an increasingly pressing issue after the expansion through the major continents by 14,600 years ago.
A changing global climate immediately preceded the transition to agriculture, so researchers have also explored a connection between the two events. Since the Last Glacial Maximum of 23,000 years ago, the Earth slowly warmed. Then, from 13,000 to 11,700 years ago, the temperature in most of the Northern Hemisphere dropped suddenly in a phenomenon called the Younger Dryas. Glaciers returned in Europe, Asia, and North America. In Mesopotamia, which includes the Levant, the climate changed from warm and humid to cool and dry. The change would have occurred over decades, disrupting the usual nomadic patterns and subsistence of foragers around the world. The disruption to foragers due to the temperature shift could have been a factor in spurring a transition to agriculture. Researchers Gregory K. Dow and colleagues (2009) believe that foraging bands would have clustered in the new resource-rich places where people started to direct their labor to farming the limited area. After the Younger Dryas ended, people expanded out of the clusters with their agricultural knowledge (Figure 13.22).
The double threat of the limitation of human continental expansion and the sudden global climate change may have placed bands in peril as more populations outpaced their environment’s carrying capacity. Not only had a growing population led to increased competition with other bands, but environments worldwide had shifted to create more uncertainty. As such, it has been proposed that as people in different areas around the world faced this unpredictable situation, they became the independent inventors of agriculture.
Agriculture around the World
Due to global changes to the human experience starting from 12,000 years ago, it has been suggested that cultures with no knowledge of each other turned toward intensely farming their local resources (see Figure 13.22). It is proposed that the first farmers engaged in artificial selection of their domesticates to enhance useful traits over generations. The switch to agriculture took time and effort with no guarantee of success and constant challenges (e.g. fires, droughts, diseases, and pests). The regions with the most widespread impact in the face of these obstacles became the primary centers of agriculture (Figure 13.23; Fuller 2010):
- Mesopotamia: The Fertile Crescent from the Tigris and Euphrates rivers through the Levant was where bands started to domesticate plants and animals around 12,000 years ago. The connection between the development of agriculture and the Younger Dryas was especially strong here. Farmed crops included wheat, barley, peas, and lentils. This was also where cattle, pigs, sheep, and goats were domesticated.
- South and East Asia: Multiple regions across this land had varieties of rice, millet, and soybeans by 10,000 years ago. Pigs were farmed with no connection to Mesopotamia. Chickens were also originally from this region, bred for fighting first and food second.
- New Guinea: Agriculture started here 10,000 years ago. Bananas, sugarcane, and taro were native to this island. Sweet potatoes were brought back from voyages to South America around the year C.E. 1000. No known animal farming occurred here.
- Mesoamerica: Agriculture from Central Mexico to northern South America also occurred from 10,000 years ago; it was also only plant based. Maize was a crop bred from teosinte grass, which has become one of the global staples. Beans, squash, and avocados were also grown in this region.
- The Andes: Starting around 8,000 years ago, local domesticated plants started with squash but later included potatoes, tomatoes, beans, and quinoa. Maize was brought down from Mesoamerica. The main farm animals were llamas, alpacas, and guinea pigs.
- Sub-Saharan Africa: This region went through a change 5,000 years ago called the Bantu expansion. The Bantu agriculturalists were established in West Central Africa and then expanded south and east. Native varieties of rice, yams, millet, and sorghum were grown across this area. Cattle were also domesticated here.
- Eastern North America: This region was the last major independent agriculture center, from 4,000 years ago. Squash and sunflower are the produce from this region that are most known today, though sumpweed and pitseed goosefoot were also farmed. Hunting was still the main source of animal products.
By 5,000 years ago, our species was well within the Neolithic Revolution. Agriculturalists spread to neighboring parts of the world with their domesticates, further expanding the use of this subsistence strategy. From this point, the human species changed from being primarily foragers to primarily agriculturalists with skilled control of their environments. The planet changed from mostly unaffected by human presence to being greatly transformed by humans. The revolution took millennia, but it was a true revolution as our species’ lifestyle was dramatically reshaped.
Cultural Effects of Agriculture
The worldwide adoption of agriculture altered the course of human culture and history forever. The core change in human culture due to agriculture is the move toward not moving: rather than live a nomadic lifestyle, farmers had to remain in one area to tend to their crops and livestock. The term for living bound to a certain location is sedentarism. This led to new aspects of life that were uncommon among foragers: the construction of permanent shelters and agricultural infrastructure, such as fields and irrigation, plus the development of storage technology, such as pottery, to preserve extra resources in case of future instability.
The high productivity of successful agriculture sparked further changes (Smith 2009). It is argued that since successful agriculture produced a much greater amount of food and other resources per unit of land compared to foraging, the population growth rate skyrocketed. The surplus of a bountiful harvest also provided insurance for harder times, reducing the risk of famine. Changes happened to society as well. With a few farming households producing enough food to feed many others, other people could focus on other tasks. So began specialization into different occupations such as craftspeople, traders, religious figures, and artists, spurring innovation in these areas as people could now devote time and effort toward specific skills. These interdependent people would settle an area together for convenience. The growth of these settlements led to urbanization, the founding of cities that became the foci of human interaction (Figure 13.24).
The formation of cities led to new issues that sparked the growth of further specializations, called institutions. These are cultural constructs that exist beyond the individual and have wide control over a population. Leadership of these cities became hierarchical with different levels of rank and control. The stratification of society increased social inequality between those with more or less power over others. Under leadership, people built impressive monumental architecture, such as pyramids and palaces, that embodied the wealth and power of these early cities. Alliances could unite cities, forming the earliest states. In several regions of the world, state organization expanded into empires, wide-ranging political entities that covered a variety of cultures.
Urbanization brought new challenges as well. The concentration of sedentary peoples was ideal for infectious diseases to thrive since they could jump from person to person and even from livestock to person (Armelagos, Brown, and Turner 2005). While successful agriculture provided a large surplus of food to thwart famine, the food produced offered less diverse food sources than foragers’ diets (Cohen and Armelagos 1984; Cohen and Crane-Kramer 2007). This shift in nutrition caused other diseases to flourish among those who adopted farming, such as dental cavities and malocclusion (the misalignment of teeth caused by soft, agricultural diets). The need to extract “wisdom teeth” or third molars seen in agricultural cultures today stems from this misalignment between the environment our ancestors adapted to and our lifestyles today.
As the new disease trends show, the adoption of agriculture and the ensuing cultural changes were not entirely positive. It is also important to note that this is not an absolutely linear progression of human culture from simple to complex. In many cases, empires have collapsed and, in some cases, cities dispersed to low-density bands that rejected institutions. However, a global trend has emerged since the adoption of agriculture, wherein population and social inequality have increased, leading to the massive and influential nation-states of today.
The rise of states in Europe has a direct impact on many of this book’s topics. Science started as a European cultural practice by the upper class that became a standardized way to study the world. Education became an institution to provide a standardized path toward producing and gaining knowledge. The scientific study of human diversity, embroiled in the race concept that still haunts us today, was connected to the European slave trade and colonialism.
Also starting in Europe, the Industrial Revolution of the 19th century turned cities into centers of mass manufacturing and spurred the rapid development of inventions (Figure 13.25). In the technologically interconnected world of today, human society has reached a new level of complexity with globalization. In this system, goods are mass-produced and consumed in different parts of the world, weakening the reliance on local farms and factories. The imbalanced relationship between consumers and producers of goods further increases economic inequality.
As states based on agriculture and industry keep exerting influence on humanity today, there are people, like the Hadzabe of Tanzania, who continue to live a lifestyle centered on foraging. Due to the overwhelming force that agricultural societies exert, foragers today have been marginalized to live in the least habitable parts of the world—the areas that are not conducive to farming, such as tropical rainforests, deserts, and the Arctic (Headland et al. 1989). Foragers can no longer live in the abundant environments that humans would have enjoyed before the Neolithic Revolution. Interactions with agriculturalists are typically imbalanced, with trade and other exchanges heavily favoring the larger group. One of anthropology’s important roles today is to intelligently and humanely manage equitable interactions between people of different backgrounds and levels of influence.
Special Topic: Indigenous Land Management
Insight into the lives of past modern humans has evolved as researchers revise previous theories and establish new connections with Indigenous knowledge holders.
The outdated view of foraging held that people lived off of the land without leaving an impact on the environment. Accompanying this idea was anthropologist Marshall Sahlins’s (1968) proposal that foragers were the “original affluent society” since they were meeting basic needs and achieving satisfaction with less work hours than agriculturalists and city-dwellers. This view countered an earlier idea that foragers were always on the brink of starvation. Sahlins’s theory took hold in the public eye as an attractive counterpoint to our busy contemporary lives in which we strive to meet our endless wants.
A fruitful type of study involving researchers collaborating with Indigenous experts has found that foragers did not just live off the land with minimal effort nor were they barely surviving in unchanging environments. Instead, they shaped the landscape to their needs using labor and strategies that were more subtle than what European colonizers and subsequent researchers were used to seeing. Research from two regions shows the latest developments in understanding Indigenous land management.
In British Columbia, Canada, the bridging of scientific and Indigenous perspectives has shown that the forests of the region are not untouched wilderness but, rather, have been crafted by Indigenous peoples thousands of years ago. Forest gardens adjacent to archaeological sites show higher plant diversity than unmanaged places even after 150 years (Armstrong et al. 2021). On the coast, 3,500-year-old archaeological sites are evidence of constructed clam gardens, according to Indigenous experts (Lepofsky et al. 2015). Another project, in consultation with Elders of the T’exelc (William Lakes First Nation) in British Columbia, introduced researchers to explanations of how forests were managed before the practice was disrupted by European colonialism (Copes-Gerbitz et al. 2021). Careful management of controlled fires reduced the density of the forest to favor plants such as raspberries and allow easier movement through the landscape.
Similarly, the study of landscapes in Australia, in consultation with Aboriginal Australians today, shows that areas previously considered wilderness by scientists were actually the result of controlling fauna and fires. The presence of grasslands with adjacent forests were purposely constructed to attract kangaroos for hunting (Gammage 2008). People also managed other animal and insect life, from emus to caterpillars. In Tasmania, a shift from productive grassland to wildfire-prone rainforest occurred after Aboriginal Australian land management was replaced by British colonial rule (Fletcher, Hall, and Alexander 2021). The site of Budj Bim of the Gunditjmara people has archaeological features of aquaculture, or the farming of fish, that date back 6,600 years (McNiven et al. 2012; McNiven et al. 2015). These examples show that Indigenous knowledge of how to manipulate the environment may be invaluable at the state level, such as by creating an Aboriginal ranger program to guide modern land management.
The Future of Humanity
A common question stemming from understanding human evolution is: What will the genetic and biological traits of our species be hundreds of thousands of years in the future? When faced with this question, people tend to think of directional selection. Maybe our braincases will be even larger, resembling the large-headed and small-bodied aliens of science fiction (Figure 13.26). Or, our hands could be specialized for interacting with our touch-based technology with less risk of repetitive injury. These ideas do not stand up to scrutiny. Since natural selection is based on adaptations that increase reproductive success, any directional change must be due to a higher rate of producing successful offspring compared to other alleles. Larger brains and more agile fingers would be convenient to possess, but they do not translate into an increase in the underlying allele frequencies.
Scientists are hesitant to professionally speculate on the unknowable, and we will never know what is in store for our species one thousand or one million years from now, but there are two trends in human evolution that may carry on into the future: increased genetic variation and a reduction in regional differences.
Rather than a directional change, genetic variation in our species could expand. Our technology can protect us from extreme environments and pathogens, even if our biological traits are not tuned to handle these stressors. The rapid pace of technological advancement means that biological adaptations will become less and less relevant to reproductive success, so nonbeneficial genetic traits will be more likely to remain in the gene pool. Biological anthropologist Jay T. Stock (2008) views environmental stress as needing to defeat two layers of protection before affecting our genetics. The first layer is our cultural adaptations. Our technology and knowledge can reduce pressure on one’s genotype to be “just right” to pass to the next generation. The second defense is our flexible physiology, such as our acclimatory responses. Only stressors not handled by these powerful responses would then cause natural selection on our alleles. These shields are already substantial, and cultural adaptations will only keep increasing in strength.
The increasing ability to travel far from one’s home region means that there will be a mixing of genetic variation on a global level in the future of our species. In recent centuries, gene flow of people around the world has increased, creating admixture in populations that had been separated for tens of thousands of years. For skin color, this means that populations all around the world could exhibit the whole range of skin colors, rather than the current pattern of decreasing melanin pigment farther from the equator. The same trend of intermixing would apply to all other traits, such as blood types. While our genetics will become more varied, the variation will be more intermixed instead of regionally isolated.
Our distant descendants will not likely be dextrous ultraintellectuals; more likely, they will be a highly variable and mobile species supported by novel cultural adaptations that make up for any inherited biological limitations. Technology may even enable the editing of DNA directly, changing these trends. With the uncertainty of our future, these are just the best-educated guesses for now. Our future is open and will be shaped little by little by the environment, our actions, and the actions of our descendants.
Summary
Modern Homo sapiens is the species that took the hominin lifestyle the furthest to become the only living member of that lineage. The largest factor that allowed us to persist while other hominins went extinct was likely our advanced ability to culturally adapt to a wide variety of environments. Our species, with its skeletal and behavioral traits, was well-suited to be generalist-specialists who successfully foraged across most of the world’s environments. The biological basis of this adaptation was our reorganized brain that facilitated innovation in cultural adaptations and intelligence for leveraging our social ties and finding ways to acquire resources from the environment. As the brain’s ability increased, it shaped the skull by reducing the evolutionary pressure to have large teeth and robust cranial bones to produce the modern Homo sapiens face.
Our ability to be generalist-specialists is seen in the geographical range that modern Homo sapiens covered in 300,000 years. In Africa, our species formed from multiregional gene flow that loosely connected archaic humans across the continent. People then expanded out to the rest of the continental Eurasia and even further to the Americas.
For most of our species’s existence, foraging was the general subsistence strategy within which people specialized to culturally adapt to their local environment. With omnivorousness and mobility, people found ways to extract and process resources, shaping the environment in return. When resource uncertainty hit the species, people around the world focused on agriculture to have a firmer control of sustenance. The new strategy shifted human history toward exponential growth and innovation, leading to our high dependence on cultural adaptations today.
While a cohesive image of our species has formed in recent years, there is still much to learn about our past. The work of many driven researchers shows that there are amazing new discoveries made all the time that refine our knowledge of human evolution. Technological innovations such as DNA analysis enable scientists to approach lingering questions from new angles. The answers we get allow us to ask even more insightful questions that will lead us to the next revelation. Like the pink limestone strata at Jebel Irhoud, previous effort has taken us so far and you are now ready to see what the next layer of discovery holds.
Hominin Species Summary
|
Hominin |
Modern Homo sapiens |
|
Dates |
315,000 years ago to present |
|
Region(s) |
Starting in Africa, then expanding around the world |
|
Famous discoveries |
Cro-Magnon individuals, discovered 1868 in Dordogne, France. Otzi the Ice Man, discovered 1991 in the Alps between Austria and Italy. Kennewick man, discovered 1996 in Washington state. |
|
Brain size |
1400 cc average |
|
Dentition |
Extremely small with short cusps. |
|
Cranial features |
An extremely globular brain case and gracile features throughout the cranium. The mandibular symphysis forms a chin at the anterior-most point. |
|
Postcranial features |
Gracile skeleton adapted for efficient bipedal locomotion at the expense of the muscular strength of most other large primates. |
|
Culture |
Extremely extensive and varied culture with many spoken and written languages. Art is ubiquitous. Technology is broad in complexity and impact on the environment. |
|
Other |
The only living hominin. Chimpanzees and bonobos are the closest living relatives. |
Review Questions
- What are the skeletal and behavioral traits that define modern Homo sapiens? What are the evolutionary explanations for its presence?
- What are some creative ways that researchers have learned about the past by studying fossils and artifacts?
- How do the discoveries mentioned in “First Africa, Then the World” fit the Assimilation model?
- What is foraging? What adaptations do we have for this subsistence strategy? Could you train to be a skilled forager?
- What are aspects of your life that come from dependence on agriculture and its cultural effects? Where did the ingredients of your favorite foods originate from?
Key Terms
African multiregionalism: The idea that modern Homo sapiens evolved as a complex web of small regional populations with sporadic gene flow among them.
Agriculture: The mass production of resources through farming and domestication.
Aquaculture: The farming of fish using techniques such as trapping, channels, and artificial ponds.
Assimilation hypothesis: Current theory of modern human origins stating that the species evolved first in Africa and interbred with archaic humans of Europe and Asia.
Atlatl: A handheld spear thrower that increased the force of thrown projectiles.
Band: A small group of people living together as foragers.
Beringia: Ancient landmass that connected Siberia and Alaska. The ancestors of Indigenous Americans would have crossed this area to reach the Americas.
Carrying capacity: The amount of organisms that an environment can reliably support.
Coastal Route model: Theory that the first Paleoindians crossed to the Americas by following the southern coast of Beringia.
Early Modern Homo sapiens, Early Anatomically Modern Human: Terms used to refer to transitional fossils between archaic and modern Homo sapiens that have a mosaic of traits. Humans like ourselves, who mostly lack archaic traits, are referred to as Late Modern Homo sapiens and simply Anatomically Modern Humans.
Egalitarian: Human organization without strict ranks. Foraging societies tend to be more egalitarian than those based on other subsistence strategies.
Foraging: Lifestyle consisting of frequent movement through the landscape and acquiring resources with minimal storage capacity.
Generalist-specialist niche: The ability to survive in a variety of environments by developing local expertise. Evolution toward this niche may have been what allowed modern Homo sapiens to expand past the geographical range of other human species.
Globalization: A recent increase in the interconnectedness and interdependence of people that is facilitated with long-distance networks.
Globular: Having a rounded appearance. Increased globularity of the braincase is a trait of modern Homo sapiens.
Gracile: Having a smooth and slender quality; the opposite of robust.
Holocene: The epoch of the Cenozoic Era starting around 12,000 years ago and lasting arguably through the present.
Ice-Free Corridor model: Theory that the first Native Americans crossed to the Americas through a passage between glaciers.
Institutions: Long-lasting and influential cultural constructs. Examples include government, organized religion, academia, and the economy.
Last Glacial Maximum: The time 23,000 years ago when the most recent ice age was the most intense.
Later Stone Age: Time period following the Middle Stone Age with a diversification in tool types, starting around 50,000 years ago.
Levant: The eastern coast of the Mediterranean. The site of early modern human expansion from Africa and later one of the centers of agriculture.
Megafauna: Large ancient animals that may have been hunted to extinction by people around the world.
Mental eminence: The chin on the mandible of modern H. sapiens. One of the defining traits of our species.
Microlith: Small stone tool found in the Later Stone Age; also called a bladelet.
Middle Stone Age: Time period known for Mousterian lithics that connects African archaic to modern Homo sapiens.
Monumental architecture: Large and labor-intensive constructions that signify the power of the elite in a sedentary society. A common type is the pyramid, a raised crafted structure topped with a point or platform.
Mosaic: Composed from a mix or composite of traits.
Neolithic Revolution: Time of rapid change to human cultures due to the invention of agriculture, starting around 12,000 years ago.
Ochre: Iron-based mineral pigment that can be a variety of yellows, reds, and browns. Used by modern human cultures worldwide since at least 80,000 years ago.
Sahul: Ancient landmass connecting New Guinea and Australia.
Sedentarism: Lifestyle based on having a stable home area; the opposite of nomadism.
Southern Dispersal model: Theory that modern H. sapiens expanded from East Africa by crossing the Red Sea and following the coast east across Asia.
Subsistence strategy: The method an organism uses to find nourishment and other resources.
Sunda: Ancient Asian landmass that incorporated modern Southeast Asia.
Supraorbital torus: The bony brow ridge across the top of the eye orbits on many hominin crania.
Upper Paleolithic: Time period considered synonymous with the Later Stone Age.
Urbanization: The increase of population density as people settled together in cities.
Wallacea: Archipelago southeast of Sunda with different biodiversity than Asia.
Younger Dryas: The rapid change in global climate—notably a cooling of the Northern Hemisphere—13,000 years ago.
For Further Exploration
Websites
First-person virtual tour of Lascaux cave with annotated cave art: Ministère de la Culture and Musée d’Archéologie Nationale. “Visit the cave” Lascaux website.
Online anthropology magazine articles related to paleoanthropology and human evolution: SAPIENS. “Evolution.” SAPIENS website.
Various presentations of information about hominin evolution: Smithsonian Institution. “What does it mean to be human?” Smithsonian National Museum of Natural History website.
Magazine-style articles on archaeology and paleoanthropology: ThoughtCo. “Archaeology.” ThoughtCo. Website.
Database of comparisons across hominins and primates: University of California, San Diego. “MOCA Domains.” Center for Academic Research & Training in Anthropogeny website.
Books
Engaging book that covers human-made changes to the environment with industrialization and globalization: Kolbert, Elizabeth. 2014. The Sixth Extinction: An Unnatural History. New York: Bloomsbury.
Overview of what human life was like among the environmental shifts of the Ice Age: Woodward, Jamie. 2014. The Ice Age: A Very Short Introduction. Oxford: OUP Press.
Articles
Recent review paper about the current state of paleoanthropology research: Stringer, C. 2016. “The Origin and Evolution of Homo sapiens.” Philosophical Transactions of the Royal Society B 371 (1698).
Overview of the history of American paleoanthropology and the many debates that have occurred over the years: Trinkaus, E. 2018. “One Hundred Years of Paleoanthropology: An American Perspective.” American Journal of Physical Anthropology 165 (4): 638–651.
Amazing magazine article that synthesizes hominin evolution and why it is important to study this subject: Wheelwright, Jeff. 2015. “Days of Dysevolution.” Discover 36 (4): 33–39.
Fascinating research on Ötzi, a mummy from 5,000 years ago: Wierer, Ursula, Simona Arrighi, Stefano Bertola, Günther Kaufmann, Benno Baumgarten, Annaluisa Pedrotti, Patrizia Pernter, and Jacques Pelegrin. 2018. “The Iceman’s Lithic Toolkit: Raw Material, Technology, Typology and Use.” PLOS One 13 (6): e0198292. https://doi.org/10.1371/journal.pone.0198292.
Documentaries
PBS NOVA series covering the expansion of modern Homo sapiens and interbreeding with archaic humans: Brown, Nicholas, dir. 2015. First Peoples. Edmonton: Wall to Wall Television. Amazon Prime Video.
PBS NOVA special featuring the footprints found in White Sands National Park: Falk, Bella, dir. 2016. Ice Age Footprints. Boston: Windfall Films. https://www.pbs.org/wgbh/nova/video/ice-age-footprints/.
PBS NOVA special about how modern humans evolved adaptations to different environments. Shows how present-day people live around the world: Thompson, Niobe, dir. 2016. Great Human Odyssey. Edmonton: Clearwater Documentary. https://www.pbs.org/wgbh/nova/evolution/great-human-odyssey.html.
References
Araujo, Bernardo B. A., Luiz Gustavo R. Oliveira-Santos, Matheus S. Lima-Ribeiro, José Alexandre F. Diniz-Filho, and Fernando A. S. Fernandez. 2017. “Bigger Kill Than Chill: The Uneven Roles of Humans and Climate on Late Quaternary Megafaunal Extinctions.” Quaternary International 431: 216–222.
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Acknowledgments
I could not have undertaken this project without the help of many who got me to where I am today. I extend sincere thank yous to the many colleagues and former students who have inspired me to keep learning and talking about anthropology. Thank you also to all who are involved in this textbook project. The anonymous reviewers truly sparked improvements to the chapter. Lastly, the staff of Starbucks #5772 also contributed immensely to this text.
Keith Chan, Ph.D., Grossmont-Cuyamaca Community College District and MiraCosta College
This chapter is a revision from "Chapter 12: Modern Homo sapiens” by Keith Chan. In Explorations: An Open Invitation to Biological Anthropology, first edition, edited by Beth Shook, Katie Nelson, Kelsie Aguilera, and Lara Braff, which is licensed under CC BY-NC 4.0.
Learning Objectives
- Identify the skeletal and behavioral traits that represent modern Homo sapiens.
- Critically evaluate different types of evidence for the origin of our species in Africa and our expansion around the world.
- Understand how the human lifestyle changed when people transitioned from foraging to agriculture.
- Hypothesize how human evolutionary trends may continue into the future.
The walls of a pink limestone cave in the hillside of Jebel Irhoud jutted out of the otherwise barren landscape of the Moroccan desert (Figure 13.1). Miners had excavated the cave in the 1960s, revealing some fossils. In 2007, a re-excavation of the site became a momentous occasion for science. A fossil cranium unearthed by a team of researchers was barely visible to the untrained eye. Just the fossil’s robust brows were peering out of the rock. This research team from the Max Planck Institute for Evolutionary Anthropology was the latest to explore the ancient human presence in this part of North Africa after a find by miners in 1960. Excavating near the first discovery, the researchers wanted to learn more about how Homo sapiens lived far from East Africa, where we thought our species originated.
The scientists were surprised when they analyzed the cranium, named Irhoud 10, and other fossils. Statistical comparisons with other human crania concluded that the Irhoud face shapes were typical of recent modern humans while the braincases matched ancient modern humans. Based on the findings of other scientists, the team expected these modern Homo sapiens fossils to be around 200,000 years old. Instead, dating revealed that the cranium had been buried for around 315,000 years.
Together, the modern-looking facial dimensions and the older date reshaped the interpretation of our species: modern Homo sapiens. Some key evolutionary changes from the archaic Homo sapiens (described in Chapter 11) to our species today happened 100,000 years earlier than we had thought and across the vast African continent rather than concentrated in its eastern region.
This revelation in the study of modern Homo sapiens is just one of the latest in this continually advancing area of biological anthropology. Researchers today are still discovering amazing fossils and ingenious ways to collect data and test hypotheses about our past. Through the collective work of many scientists, we are building an overall theory of modern human origins.
Defining Modernity
What defines modern Homo sapiens when compared to archaic Homo sapiens? Modern humans, like you and me, have a set of derived traits that are not seen in archaic humans or any other hominin. As with other transitions in hominin evolution, such as increasing brain size and bipedal ability, modern traits do not appear fully formed or all at once. In other words, the first modern Homo sapiens was not just born one day from archaic parents. The traits common to modern Homo sapiens appeared in a mosaic manner: gradually and out of sync with one another. There are two areas to consider when tracking the complex evolution of modern human traits. One is the physical change in the skeleton. The other is behavior inferred from the size and shape of the cranium and material culture evidence.
Skeletal Traits
The skeleton of modern Homo sapiens is less robust than that of archaic Homo sapiens. In other words, the modern skeleton is gracile, meaning that the structures are thinner and smoother. Differences related to gracility in the cranium are seen in the braincase, the face, and the mandible. There are also broad differences in the rest of the skeleton.
Cranial Traits
Several elements of the braincase differ between modern and archaic Homo sapiens. Overall, the shape is much rounder, or more globular, on a modern skull (Lieberman, McBratney, and Krovitz 2002; Neubauer, Hublin, and Gunz 2018; Pearson 2008; Figure 13.2). You can feel the globularity of your own modern human skull. Feel the height of your forehead with the palm of your hand. Viewed from the side, the tall vertical forehead of a modern Homo sapiens stands out when compared to the sloping archaic version. This is because the frontal lobe of the modern human brain is larger than the one in archaic humans, and the skull has to accommodate the expansion. The vertical forehead reduces a trait that is common to all other hominins: the brow ridge or supraorbital torus. The parietal lobes of the brain and the matching parietal bones on either side of the skull both bulge outward more in modern humans. At the back of the skull, the archaic occipital bun is no longer present. Instead, the occipital region of the modern human cranium has a derived tall and smooth curve, again reflecting the globular brain inside.
The trend of shrinking face size across hominins reaches its extreme with our species as well. The facial bones of a modern Homo sapiens are extremely gracile compared to all other hominins (Lieberman, McBratney, and Krovitz 2002). Continuing a trend in hominin evolution, technological innovations kept reducing the importance of teeth in reproductive success (Lucas 2007). As natural selection favored smaller and smaller teeth, the surrounding bone holding these teeth also shrank.
Related to smaller teeth, the mandible is also gracile in modern humans when compared to archaic humans and other hominins. Interestingly, our mandibles have pulled back so far from the prognathism of earlier hominins that we gained an extra structure at the most anterior point, called the mental eminence. You know this structure as the chin. At the skeletal level, it resembles an upside-down “T” at the centerline of the mandible (Pearson 2008). Looking back at archaic humans, you will see that they all lack a chin. Instead, their mandibles curve straight back without a forward point. What is the chin for and how did it develop? Flora Gröning and colleagues (2011) found evidence of the chin’s importance by simulating physical forces on computer models of different mandible shapes. Their results showed that the chin acts as structural support to withstand strain on the otherwise gracile mandible.
Postcranial Gracility
The rest of the modern human skeleton is also more gracile than its archaic counterpart. The differences are clear when comparing a modern Homo sapiens with a cold-adapted Neanderthal (Sawyer and Maley 2005), but the trends are still present when comparing modern and archaic humans within Africa (Pearson 2000). Overall, a modern Homo sapiens postcranial skeleton has thinner cortical bone, smoother features, and more slender shapes when compared to archaic Homo sapiens (Figure 13.3). Comparing whole skeletons, modern humans have longer limb proportions relative to the length and width of the torso, giving us lankier outlines.
Why is our skeleton so gracile compared to those of other hominins? Natural selection can drive the gracilization of skeletons in several ways (Lieberman 2015). A slender frame is believed to be adapted for the efficient long-distance running ability that started with Homo erectus. Furthermore, it is argued that slenderness is a genetic adaptation for cooling an active body in hotter climates, which aligns with the ample evidence that Africa was the home continent of our species.
Behavioral Modernity
Aside from physical differences in the skeleton, researchers have also uncovered evidence of behavioral changes associated with increased cultural complexity from archaic to modern humans. How did cultural complexity develop? Two investigations into this question are archaeology and the analysis of reconstructed brains.
Archaeology tells us much about the behavioral complexity of past humans by interpreting the significance of material culture. In terms of advanced culture, items created with an artistic flair, or as decoration, speak of abstract thought processes (Figure 13.4). The demonstration of difficult artistic techniques and technological complexity hints at social learning and cooperation as well. According to paleoanthropologist John Shea (2011), one way to track the complexity of past behavior through artifacts is by measuring the variety of tools found together. The more types of tools constructed with different techniques and for different purposes, the more modern the behavior. Researchers are still working on an archaeological way to measure cultural complexity that is useful across time and place.
The interpretation of brain anatomy is another promising approach to studying the evolution of human behavior. When looking at investigations on this topic in modern Homo sapiens brains, researchers found a weak association between brain size and test-measured intelligence (Pietschnig et al. 2015). Additionally, they found no association between intelligence and biological sex. These findings mean that there are more significant factors that affect tested intelligence than just brain size. Since the sheer size of the brain is not useful for weighing intelligence within a species, paleoanthropologists are instead investigating the differences in certain brain structures. The differences in organization between modern Homo sapiens brains and archaic Homo sapiens brains may reflect different cognitive priorities that account for modern human culture. As with the archaeological approach, new discoveries will refine what we know about the human brain and apply that knowledge to studying the distant past.
Taken together, the cognitive abilities in modern humans may have translated into an adept use of tools to enhance survival. Researchers Patrick Roberts and Brian A. Stewart (2018) call this concept the generalist-specialist niche: our species is an expert at living in a wide array of environments, with populations culturally specializing in their own particular surroundings. The next section tracks how far around the world these skeletal and behavioral traits have taken us.
First Africa, Then the World
What enabled modern Homo sapiens to expand its range further in 300,000 years than Homo erectus did in 1.5 million years? The key is the set of derived biological traits from the last section. It is theorized that the gracile frame and neurological anatomy allowed modern humans to survive and even flourish in the vastly different environments they encountered. Based on multiple types of evidence, the source of all of these modern humans was Africa. Instead of originating from just one location, evidence shows that modern Homo sapiens evolution occurred in a complex gene flow network across Africa, a concept called African multiregionalism (Scerri et al. 2018).
This section traces the origin of modern Homo sapiens and the massive expansion of our species across all of the continents (except Antarctica) by 12,000 years ago. While modern Homo sapiens first shared geography with archaic humans, modern humans eventually spread into lands where no human had gone before. Figure 13.5 shows the broad routes that our species took expanding around the world. I encourage you to make your own timeline with the dates in this part to see the overall trends.
Modern Homo sapiens Biology and Culture in Africa
We start with the ample fossil evidence supporting the theory that modern humans originated in Africa during the Middle Pleistocene, having evolved from African archaic Homo sapiens. The earliest dated fossils considered to be modern actually have a mosaic of archaic and modern traits, showing the complex changes from one type to the other. Experts have various names for these transitional fossils, such as Early Modern Homo sapiens or Early Anatomically Modern Humans. However they are labeled, the presence of some modern traits means that they illustrate the origin of the modern type. Three particularly informative sites with fossils of the earliest modern Homo sapiens are Jebel Irhoud, Omo, and Herto.
Recall from the start of the chapter that the most recent finds at Jebel Irhoud are now the oldest dated fossils that exhibit some facial traits of modern Homo sapiens. Besides Irhoud 10, the cranium that was dated to 315,000 years ago (Hublin et al. 2017; Richter et al. 2017), there were other fossils found in the same deposit that we now know are from the same time period. In total there are at least five individuals, representing life stages from childhood to adulthood. These fossils form an image of high variation in skeletal traits. For example, the skull named Irhoud 1 has a primitive brow ridge, while Irhoud 2 and Irhoud 10 do not (Figure 13.6). The braincases are lower than what is seen in the modern humans of today but higher than in archaic Homo sapiens. The teeth also have a mix of archaic and modern traits that defy clear categorization into either group.
Research separated by nearly four decades uncovered fossils and artifacts from the Kibish Formation in the Lower Omo Valley in Ethiopia. These Omo Kibish hominins were represented by braincases and fragmented postcranial bones of three individuals found kilometers apart, dating back to around 233,000 years ago (Day 1969; McDougall, Brown, and Fleagle 2005; Vidal et al. 2022). One interesting finding was the variation in braincase size between the two more-complete specimens: while the individual named Omo I had a more globular dome, Omo II had an archaic-style long and low cranium.
Also in Ethiopia, a team led by Tim White (2003) excavated numerous fossils at Herto. There were fossilized crania of two adults and a child, along with fragments of more individuals. The dates ranged between 160,000 and 154,000 years ago. The skeletal traits and stone-tool assemblage were both intermediate between the archaic and modern types. Features reminiscent of modern humans included a tall braincase and thinner zygomatic (cheek) bones than those of archaic humans (Figure 13.7). Still, some archaic traits persisted in the Herto fossils, such as the supraorbital tori. Statistical analysis by other research teams concluded that at least some cranial measurements fit just within the modern human range (McCarthy and Lucas 2014), favoring categorization with our own species.
The timeline of material culture suggests a long period of relying on similar tools before a noticeable diversification of artifacts types. Researchers label the time of stable technology shared with archaic types the Middle Stone Age, while the subsequent time of diversification in material culture is called the Later Stone Age.
In the Middle Stone Age, the sites of Jebel Irhoud, Omo, and Herto all bore tools of the same flaked style as archaic assemblages, even though they were separated by almost 150,000 years. The consistency in technology may be evidence that behavioral modernity was not so developed. No clear signs of art dating back this far have been found either. Other hypotheses not related to behavioral modernity could explain these observations. The tool set may have been suitable for thriving in Africa without further innovation. Maybe works of art from that time were made with media that deteriorated or perhaps such art was removed by later humans.
Evidence of what Homo sapiens did in Africa from the end of the Middle Stone Age to the Later Stone Age is concentrated in South African cave sites that reveal the complexity of human behavior at the time. For example, Blombos Cave, located along the present shore of the Cape of Africa facing the Indian Ocean, is notable for having a wide variety of artifacts. The material culture shows that toolmaking and artistry were more complex than previously thought for the Middle Stone Age. In a layer dated to 100,000 years ago, researchers found two intact ochre-processing kits made of abalone shells and grinding stones (Henshilwood et al. 2011). Marine snail shell beads from 75,000 years ago were also excavated (Figure 13.8; d’Errico et al. 2005). Together, the evidence shows that the Middle Stone Age occupation at Blombos Cave incorporated resources from a variety of local environments into their culture, from caves (ochre), open land (animal bones and fat), and the sea (abalone and snail shells). This complexity shows a deep knowledge of the region’s resources and their use—not just for survival but also for symbolic purposes.
On the eastern coast of South Africa, Border Cave shows new African cultural developments at the start of the Later Stone Age. Paola Villa and colleagues (2012) identified several changes in technology around 43,000 years ago. Stone-tool production transitioned from a slower process to one that was faster and made many microliths, small and precise stone tools. Changes in decorations were also found across the Later Stone Age transition. Beads were made from a new resource: fragments of ostrich eggs shaped into circular forms resembling present-day breakfast cereal O’s (d’Errico et al. 2012). These beads show a higher level of altering one’s own surroundings and a move from the natural to the abstract in terms of design.
Expansion into the Middle East and Asia
While modern Homo sapiens lived across Africa, some members eventually left the continent. These pioneers could have used two connections to the Middle East or West Asia. From North Africa, they could have crossed the Sinai Peninsula and moved north to the Levant, or eastern Mediterranean. Finds in that region show an early modern human presence. Other finds support the Southern Dispersal model, with a crossing from East Africa to the southern Arabian Peninsula through the Straits of Bab-el-Mandeb. It is tempting to think of one momentous event in which people stepped off Africa and into the Middle East, never to look back. In reality, there were likely multiple waves of movement producing gene flow back and forth across these regions as the overall range pushed east. The expanding modern human population could have thrived by using resources along the southern coast of the Arabian Peninsula to South Asia, with side routes moving north along rivers. The maximum range of the species then grew across Asia.
Modern Homo sapiens in the Middle East
Geographically, the Middle East is the ideal place for the African modern Homo sapiens population to inhabit upon expanding out of their home continent. In the Eastern Mediterranean coast of the Levant, there is a wealth of skeletal and material culture linked to modern Homo sapiens. Recent discoveries from Saudi Arabia further add to our view of human life just beyond Africa.
The Caves of Mount Carmel in present-day Israel have preserved skeletal remains and artifacts of modern Homo sapiens, the first-known group living outside Africa. The skeletal presence at Misliya Cave is represented by just part of the left upper jaw of one individual, but it is notable for being dated to a very early time, between 194,000 and 177,000 years ago (Hershkovitz et al. 2018). Later, from 120,000 to 90,000 years ago, fossils of multiple individuals across life stages were found in the caves of Es-Skhul and Qafzeh (Shea and Bar-Yosef 2005). The skeletons had many modern Homo sapiens traits, such as globular crania and more gracile postcranial bones when compared to Neanderthals. Still, there were some archaic traits. For example, the adult male Skhul V also possessed what researchers Daniel Lieberman, Osbjorn Pearson, and Kenneth Mowbray (2000) called marked or clear occipital bunning. Also, compared to later modern humans, the Mount Carmel people were more robust. Skhul V had a particularly impressive brow ridge that was short in height but sharply jutted forward above the eyes (Figure 13.9). The high level of preservation is due to the intentional burial of some of these people. Besides skeletal material, there are signs of artistic or symbolic behavior. For example, the adult male Skhul V had a boar’s jaw on his chest. Similarly, Qafzeh 11, a juvenile with healed cranial trauma, had an impressive deer antler rack placed over his torso (Figure 13.10; Coqueugniot et al. 2014). Perforated seashells colored with ochre, mineral-based pigment, were also found in Qafzeh (Bar-Yosef Mayer, Vandermeersch, and Bar-Yosef 2009).
One remaining question is, what happened to the modern humans of the Levant after 90,000 years ago? Another site attributed to our species did not appear in the region until 47,000 years ago. Competition with Neanderthals may have accounted for the disappearance of modern human occupation since the Neanderthal presence in the Levant lasted longer than the dates of the early modern Homo sapiens. John Shea and Ofer Bar-Yosef (2005) hypothesized that the Mount Carmel modern humans were an initial expansion from Africa that failed. Perhaps they could not succeed due to competition with the Neanderthals who had been there longer and had both cultural and biological adaptations to that environment.
Modern Homo sapiens of China
A long history of paleoanthropology in China has found ample evidence of modern human presence. Four notable sites are the caves at Fuyan, Liujiang, Tianyuan, and Zhoukoudian. In the distant past, these caves would have been at least seasonal shelters that unintentionally preserved evidence of human presence for modern researchers to discover.
At Fuyan Cave in Southern China, paleoanthropologists found 47 adult teeth associated with cave formations dated to between 120,000 and 80,000 years ago (Liu et al. 2015). It is currently the oldest-known modern human site in China, though other researchers question the validity of the date range (Michel et al. 2016). The teeth have the small size and gracile features of modern Homo sapiens dentition.
The fossil Liujiang (or Liukiang) hominin (67,000 years ago) has derived traits that classified it as a modern Homo sapiens, though primitive archaic traits were also present. In the skull, which was found nearly complete, the Liujiang hominin had a taller forehead than archaic Homo sapiens but also had an enlarged occipital region (Figure 13.11; Brown 1999; Wu et al. 2008). Other parts of the skeleton also had a mix of modern and archaic traits: for example, the femur fragments suggested a slender length but with thick bone walls (Woo 1959).
Another Chinese site to describe here is the one that has been studied the longest. In the Zhoukoudian Cave system (Figure 13.12), where Homo erectus and archaic Homo sapiens have also been found, there were three crania of modern Homo sapiens. These crania, which date to between 34,000 and 10,000 years ago, were all more globular than those of archaic humans but still lower and longer than those of later modern humans (Brown 1999; Harvati 2009). When compared to one another, the crania showed significant differences from one another. Comparison of cranial measurements to other populations past and present found no connection with modern East Asians, again showing that human variation was very different from what we see today.
Crossing to Australia
Expansion of the first modern human Asians, still following the coast, eventually entered an area that researchers call Sunda before continuing on to modern Australia. Sunda was a landmass made up of the modern-day Malay Peninsula, Sumatra, Java, and Borneo. Lowered sea levels connected these places with land bridges, making them easier to traverse. Proceeding past Sunda meant navigating Wallacea, the archipelago that includes the Indonesian islands east of Borneo. In the distant past, there were many megafauna, large animals that migrating humans would have used for food and materials (such as utilizing animals’ hides and bones). Further southeast was another landmass called Sahul, which included New Guinea and Australia as one contiguous continent. Based on fossil evidence, this land had never seen hominins or any other primates before modern Homo sapiens arrived. Sites along this path offer clues about how our species handled the new environment to live successfully as foragers.
The skeletal remains at Lake Mungo, land traditionally owned by Mutthi Mutthi, Ngiampaa, and Paakantji peoples, are the oldest known in the continent. The now-dry lake was one of a series located along the southern coast of Australia in New South Wales, far from where the first people entered from the north (Barbetti and Allen 1972; Bowler et al. 1970). Two individuals dating to around 40,000 years ago show signs of artistic and symbolic behavior, including intentional burial. The bones of Lake Mungo 1 (LM1), an adult female, were crushed repeatedly, colored with red ochre, and cremated (Bowler et al. 1970). Lake Mungo 3 (LM3), a tall, older male with a gracile cranium but robust postcranial bones, had his fingers interlocked over his pelvic region (Brown 2000).
Kow Swamp, within traditional Yorta Yorta land also in southern Australia, contained human crania that looked distinctly different from the ones at Lake Mungo (Durband 2014; Thorne and Macumber 1972). The crania, dated between 9,000 and 20,000 years ago, had extremely robust brow ridges and thick bone walls, but these were paired with globular features on the braincase (Figure 13.13).
While no fossil humans have been found at the Madjedbebe rock shelter in the North Territory of Australia, more than 10,000 artifacts found there show both behavioral modernity and variability (Clarkson et al. 2017). They include a diverse array of stone tools and different shades of ochre for rock art, including mica-based reflective pigment (similar to glitter). These impressive artifacts are as far back as 56,000 years old, providing the date for the earliest-known presence of humans in Australia.
From the Levant to Europe
The first modern human expansion into Europe occurred after other members of our species settled in East Asia and Australia. As the evidence from the Levant suggests, modern human movement to Europe may have been hampered by the presence of Neanderthals. It is suggested that another obstacle was the colder climate, which was incompatible with the biology of modern Homo sapiens from Africa, as they were adapted to high temperatures and ultraviolet radiation. Still, by 40,000 years ago, modern Homo sapiens had a detectable presence. This time was also the start of the Later Stone Age or Upper Paleolithic, when there was an expansion in cultural complexity. There is a wealth of evidence from this region due to a Western bias in research, the proximity of these findings to Western scientific institutions, and the desire of Western scientists to explore their own past.
In Romania, the site of Peștera cu Oase (Cave of Bones) had the oldest-known remains of modern Homo sapiens in Europe, dated to around 40,000 years ago (Trinkaus et al. 2003a). Among the bones and teeth of many animals were the fragmented cranium of one person and the mandible of another (the two bones did not fit each other). Both bones have modern human traits similar to the fossils from the Middle East, but they also had Neanderthal traits. Oase 1, the mandible, had a mental eminence but also extremely large molars (Trinkaus et al. 2003b). This mandible has yielded DNA that surprisingly is equally similar to DNA from present-day Europeans and Asians (Fu et al. 2015). This means that Oase 1 was not the direct ancestor of modern Europeans. The Oase 2 cranium has the derived traits of reduced brow ridges along with archaic wide zygomatic cheekbones and an occipital bun (Figure 13.14; Rougier et al. 2007).
Dating to around 26,000 years ago, Předmostí near Přerov in the Czech Republic was a site where people buried over 30 individuals along with many artifacts. Eighteen individuals were found in one mass burial area, a few covered by the scapulae of woolly mammoths (Germonpré, Lázničková-Galetová, and Sablin 2012). The Předmostí crania were more globular than those of archaic humans but tended to be longer and lower than in later modern humans (Figure 13.15; Velemínská et al. 2008). The height of the face was in line with modern residents of Central Europe. There was also skeletal evidence of dog domestication, such as the presence of dog skulls with shorter snouts than in wild wolves (Germonpré, Lázničková-Galetová, and Sablin et al. 2012). In total, Předmostí could have been a settlement dependent on mammoths for subsistence and the artificial selection of early domesticated dogs.
The sequence of modern Homo sapiens technological change in the Later Stone Age has been thoroughly dated and labeled by researchers working in Europe. Among them, the Gravettian tradition of 33,000 years to 21,000 years ago is associated with most of the known curvy female figurines, often assumed to be “Venus” figures. Hunting technology also advanced in this time with the first known boomerang, atlatl (spear thrower), and archery. The Magdalenian tradition spread from 17,000 to 12,000 years ago. This culture further expanded on fine bone tool work, including barbed spearheads and fishhooks (Figure 13.16).
Among the many European sites dating to the Later Stone Age, the famous cave art sites deserve mention. Chauvet-Pont-d'Arc Cave in southern France dates to separate Aurignacian occupations 31,000 years ago and 26,000 years ago. Over a hundred art pieces representing 13 animal species are preserved, from commonly depicted deer and horses to rarer rhinos and owls. Another French cave with art is Lascaux, which is several thousand years younger at 17,000 years ago in the Magdalenian period. At this site, there are over 6,000 painted figures on the walls and ceiling (Figure 13.17). Scaffolding and lighting must have been used to make the paintings on the walls and ceiling deep in the cave. Overall, visiting Lascaux as a contemporary must have been an awesome experience: trekking deeper in the cave lit only by torches giving glimpses of animals all around as mysterious sounds echoed through the galleries.
Special Topic: Cannibalism and Culture - Mortuary Practices in Modern Homo sapiens
Within a 2017 publication in the Journal of Archaeological Method and Theory, Saladié and Rodríguez-Hidalgo bring light to traces of early cannibalism in western Eurasia, arguing that context-specific cannibalistic practices were present throughout the Pleistocene and increased notably from the end of the Upper Palaeolithic and onward (Saladié & Rodriguez-Hidalgo, 2017). While early hominins and Neandertals are recognized in this research, the authors highlight the presence of these mortuary practices in a cluster of Homo Sapien sites. More recent research uncovers similar findings that back these claims as well, where human bones in Herto Ethiopia, Maszycka Cave Poland, and Gough’s Cave in the United Kingdom show anthropogenic defleshing and other modifications which have been interpreted as cannibalism (Pobiner, Et al. 2023). These findings suggest that cannibalistic behaviours formed a recurring aspect of modern human behaviour in certain ecological and cultural contexts.
A significant example comes from the Neolithic levels of Fontbrégua Cave in southeastern France, where Paola Villa and colleagues compared clusters of human bones with the remains of wild and domestic animals from the same sediments. The study found that human bodies were butchered, processed, and most likely eaten in a way that parallels animal carcass treatment, including the placement and timing of cut marks, dismemberment sequences, and perimortem fractures to open marrow cavities (Villa, Et al. 1986). As the assemblage comes from a primary depositional context with pristine preservation and careful excavation, the authors suggest that cannibalism is the only satisfactory explanation for the pattern of cut marks and breakage seen on the human bones.
More recent work has furthered this hypothesis for Late Upper Palaeolithic Homo sapiens, especially in Magdalenian contexts. In a 2023 study, researchers combined archeological and genetic evidence from fifty-nine Magdalenian sites, concluding that this specific culture shows an unusually high frequency of cannibalistic cases compared to earlier and later hominin groups; so much so that they identify “primary burial and cannibalism” as the two main mortuary expressions (Marsh & Bello, 2023). Additionally, new analyses from Maszycka Cave in Poland have described cut and broken human bones in patterns consistent with human consumption, reinforcing this cannibalism hypothesis (Marginedas & Saladié, 2025). Together, these studies suggest that for some Magdalenian groups, mortuary cannibalism was a habitual way of disposing of the dead, not just a one-off crisis response. At the same time, researchers emphasize that not every modified skeleton indicates blatant consumption of the dead and that ritual or symbolic perspectives must also be considered. Previously noted in chapter eleven, Ullrich’s survey of European mortuary practices presents frequent manipulations of corpses from the Palaeolithic through the Hallstatt period. Said manipulations include cut marks, dismemberment, skull fracturing, and marrow extraction (Ullrich, 2005, p. 258), which Ullrich interprets as cannibalistic rites embedded in cult ceremonies rather than everyday subsistence. In the author’s view, some Palaeolithic groups may have believed that consuming members of their community allowed them to take on the strengths, abilities, or even mental aspects of their dead member; the act of cannibalism may have functioned as a form of appropriating physical and mental powers rather than simply obtaining calories. With that, Neolithic assemblages show how careful taphonomic work can distinguish cuts linked to interpersonal violence from those associated with systemic butchery (Marginedas & Saladié, 2025). The findings seek to highlight that some Homo sapiens populations combined ritual, mortuary, and nutritional motives when processing human remains.
These past and contemporary findings are significant for future anthropology students as they shed light on biological anthropology methodology and interpretation. Archaeologists are able to distinguish between occasions when humans were handled like any other carcass and times when they were handled in more symbolic ways thanks to factors like cut mark orientation, the timing of bone breakage, and direct comparison with animal remains. Readers interested in exploring this topic further should investigate the context-specific motivations for cannibalism, like nutritional stress, warfare, funerary sites, or ritual power appropriation.
Similar archeological techniques have been used to explore behaviours of cannibalism among Indigenous Huron-Wendat populations in 1651 Canada, where human bones exhibit cutmarks, perimortem fractures, and thermal modifications (Spence & Jackson, 2014). These shared taphonomic signatures across continents reveal recurring practices under ecological stress, bridging prehistoric Europe to North American contexts. Engaging with such analytical techniques opens up new ways that archeologists and anthropologists can investigate the variability in human behaviour, from nutritional crises to mortuary rituals.
Peopling of the Americas
By 25,000 years ago, our species was the only member of Homo left on Earth. Gone were the Neanderthals, Denisovans, Homo naledi, and Homo floresiensis. The range of modern Homo sapiens kept expanding eastward into—using the name given to this area by Europeans much later—the Western Hemisphere. This section will address what we know about the peopling of the Americas, from the first entry to these continents to the rapid spread of Indigenous Americans across its varied environments.
While evidence points to an ancient land bridge called Beringia that allowed people to cross from what is now northeastern Siberia into modern-day Alaska, what people did to cross this land bridge is still being investigated. For most of the 20th century, the accepted theory was the Ice-Free Corridor model. It stated that northeast Asians (East Asians and Siberians) first expanded across Beringia inland through a passage between glaciers that opened into the western Great Plains of the United States, just east of the Rocky Mountains, around 13,000 years ago (Swisher et al. 2013). While life up north in the cold environment would have been harsh, migrating birds and an emerging forest might have provided sustenance as generations expanded through this land (Potter et al. 2018).
However, in recent decades, researchers have accumulated evidence against the Ice-Free Corridor model. Archaeologist K. R. Fladmark (1979) brought the alternate Coastal Route model into the archaeological spotlight; researcher Jon M. Erlandson has been at the forefront of compiling support for this theory (Erlandson et al. 2015). The new focus is the southern edge of the land bridge instead of its center: About 16,000 years ago, members of our species expanded along the coastline from northeast Asia, east through Beringia, and south down the Pacific Coast of North America while the inland was still sealed off by ice. The coast would have been free of ice at least part of the year, and many resources would have been found there, such as fish (e.g., salmon), mammals (e.g., whales, seals, and otters), and plants (e.g., seaweed).
South through the Americas
When the first modern Homo sapiens reached the Western Hemisphere, the spread through the Americas was rapid. Multiple migration waves crossed from North to South America (Posth et al. 2018). Our species took advantage of the lack of hominin competition and the bountiful resources both along the coasts and inland. The Americas had their own wide array of megafauna, which included woolly mammoths (Figure 13.18), mastodons, camels, horses, ground sloths, giant tortoises, and—a favorite of researchers—a two-meter-tall beaver. The reason we cannot see these amazing animals today may be that resources gained from these fauna were crucial to the survival for people over 12,000 years ago (Araujo et al. 2017). Several sites are notable for what they add to our understanding of the distant past in the Americas, including interactions with megafauna and other elements of the environment.
A 2019 discovery may allow researchers to improve theories about the peopling of the Americas. In White Sands National Park, New Mexico, 60 human footprints have been astonishingly dated to around 22,000 years ago (Bennett et al. 2021). This date and location do not match either the Ice-Free Corridor or Coastal Route models. Researchers are now working to verify the find and adjust previous models to account for the new evidence. This groundbreaking find is sparking new theories; it is another example of the fast pace of research performed on our past.
Monte Verde is a landmark site that shows that the human population had expanded down the whole vertical stretch of the Americas to Chile by 14,600 years ago. The site has been excavated by archaeologist Tom D. Dillehay and his team (2015). The remains of nine distinct edible species of seaweed at the site shows familiarity with coastal resources and relates to the Coastal Route model by showing a connection between the inland people and the sea.
Named after the town in New Mexico, the Clovis stone-tool style is the first example of a widespread culture across much of North America, between 13,400 and 12,700 years ago (Miller, Holliday, and Bright 2013). Clovis points were fluted with two small projections, one on each end of the base, facing away from the head (Figure 13.19). The stone points found at this site match those found as far as the Canadian border and northern Mexico, and from the west coast to the east coast of the United States. Fourteen Clovis sites also contained the remains of mammoths or mastodons, suggesting that hunting megafauna with these points was an important part of life for the Clovis people. After the spread of the Clovis style, it diversified into several regional styles, keeping some of the Clovis form but also developing their own unique touches.
The Big Picture: The Assimilation Hypothesis
How do researchers make sense of all of these modern Homo sapiens discoveries that cover over 300,000 years of time and stretch across every continent except Antarctica? How was modern Homo sapiens related to archaic Homo sapiens?
The Assimilation hypothesis proposes that modern Homo sapiens evolved in Africa first and expanded out but also interbred with the archaic Homo sapiens they encountered outside Africa (Figure 13.20). This hypothesis is powerful since it explains why Africa has the oldest modern human fossils, why early modern humans found in Europe and Asia bear a resemblance to the regional archaics, and why traces of archaic DNA can be found in our genomes today (Dannemann and Racimo 2018; Reich et al. 2010; Reich et al. 2011; Slatkin and Racimo 2016; Smith et al. 2017; Wall and Yoshihara Caldeira Brandt 2016).
While researchers have produced a model that satisfies the data, there are still a lot of questions for paleoanthropologists to answer regarding our origins. What were the patterns of migration in each part of the world? Why did the archaic humans go extinct? In what ways did archaic and modern humans interact? The definitive explanation of how our species started and what our ancestors did is still out there to be found. You are now in a great place to welcome the next discovery about our distant past—maybe you’ll even contribute to our understanding as well.
The Chain Reaction of Agriculture
While it may be hard to imagine today, for most of our species’ existence we were nomadic: moving through the landscape without a singular home. Instead of a refrigerator or pantry stocked with food, we procured nutrition and other resources as needed based on what was available in the environment. This section gives an overview of how the foraging lifestyle enabled the expansion of our species and how the invention of a new way of life caused a chain reaction of cultural change.
The Foraging Tradition
There are a variety of possible subsistence strategies, or methods of finding sustenance and resources. To understand our species is to understand the subsistence strategy of foraging, or the search for resources in the environment. While most (but not all) humans today live in cultures that practice agriculture (whereby we greatly shape the environment to mass produce what we need), we have spent far more time as nomadic foragers than as settled agriculturalists. As such, it has been suggested that our traits have evolved to be primarily geared toward foraging. For instance, our efficient bipedalism allows persistence-hunting across long distances as well as movement from resource to resource.
How does human foraging, also known as hunting and gathering, work? Anthropologists have used all four fields to answer this question (see Ember n.d.). Typically, people formed bands, or kin-based groups of around 50 people or less (rarely over 100). A band’s organization would be egalitarian, with a flexible hierarchy based on an individual’s age, level of experience, and relationship with others. Everyone would have a general knowledge of the skills assigned to their gender roles, rather than specializing in different occupations. A band would be able to move from place to place in the environment, using knowledge of the area to forage (Figure 13.21). In varied environments—from savannas to tropical forests, deserts, coasts, and the Arctic circle—people found sustenance needed for survival.
Humans made extensive use of the foraging subsistence strategy, but this lifestyle did have limitations. The ease of foraging depended on the richness of the environment. Due to the lack of storage, resources had to be dependably found when needed. While a bountiful environment would require just a few hours of foraging a day and could lead to a focus on one location, the level and duration of labor increased greatly in poor or unreliable environments. Labor was also needed to process the acquired resources, which contributed to the foragers’ daily schedule (Crittenden and Schnorr 2017).
The adaptations to foraging found in modern Homo sapiens may explain why our species became so successful both within Africa and in the rapid expansion around the world. Overcoming the limitations, each generation at the edge of our species’s range would have found it beneficial to expand a little further, keeping contact with other bands but moving into unexplored territory where resources were more plentiful. The cumulative effect would have been the spread of modern Homo sapiens across continents and hemispheres.
Why Agriculture?
After hundreds of thousands of years of foraging, some groups of people around 12,000 years ago started to practice agriculture. This transition, called the Neolithic Revolution, occurred at the start of the Holocene epoch. While the reasons for this global change are still being investigated, two likely co-occurring causes are a growing human population and natural global climate change.
Overcrowding could have affected the success of foraging in the environment, leading to the development of a more productive subsistence strategy (Cohen 1977). Foraging works best with low population densities since each band needs a lot of space to support itself. If too many people occupy the same environment, they deplete the area faster. The high population could exceed the carrying capacity, or number of people a location can reliably support. Reaching carrying capacity on a global level due to growing population and limited areas of expansion would have been an increasingly pressing issue after the expansion through the major continents by 14,600 years ago.
A changing global climate immediately preceded the transition to agriculture, so researchers have also explored a connection between the two events. Since the Last Glacial Maximum of 23,000 years ago, the Earth slowly warmed. Then, from 13,000 to 11,700 years ago, the temperature in most of the Northern Hemisphere dropped suddenly in a phenomenon called the Younger Dryas. Glaciers returned in Europe, Asia, and North America. In Mesopotamia, which includes the Levant, the climate changed from warm and humid to cool and dry. The change would have occurred over decades, disrupting the usual nomadic patterns and subsistence of foragers around the world. The disruption to foragers due to the temperature shift could have been a factor in spurring a transition to agriculture. Researchers Gregory K. Dow and colleagues (2009) believe that foraging bands would have clustered in the new resource-rich places where people started to direct their labor to farming the limited area. After the Younger Dryas ended, people expanded out of the clusters with their agricultural knowledge (Figure 13.22).
The double threat of the limitation of human continental expansion and the sudden global climate change may have placed bands in peril as more populations outpaced their environment’s carrying capacity. Not only had a growing population led to increased competition with other bands, but environments worldwide had shifted to create more uncertainty. As such, it has been proposed that as people in different areas around the world faced this unpredictable situation, they became the independent inventors of agriculture.
Agriculture around the World
Due to global changes to the human experience starting from 12,000 years ago, it has been suggested that cultures with no knowledge of each other turned toward intensely farming their local resources (see Figure 13.22). It is proposed that the first farmers engaged in artificial selection of their domesticates to enhance useful traits over generations. The switch to agriculture took time and effort with no guarantee of success and constant challenges (e.g. fires, droughts, diseases, and pests). The regions with the most widespread impact in the face of these obstacles became the primary centers of agriculture (Figure 13.23; Fuller 2010):
- Mesopotamia: The Fertile Crescent from the Tigris and Euphrates rivers through the Levant was where bands started to domesticate plants and animals around 12,000 years ago. The connection between the development of agriculture and the Younger Dryas was especially strong here. Farmed crops included wheat, barley, peas, and lentils. This was also where cattle, pigs, sheep, and goats were domesticated.
- South and East Asia: Multiple regions across this land had varieties of rice, millet, and soybeans by 10,000 years ago. Pigs were farmed with no connection to Mesopotamia. Chickens were also originally from this region, bred for fighting first and food second.
- New Guinea: Agriculture started here 10,000 years ago. Bananas, sugarcane, and taro were native to this island. Sweet potatoes were brought back from voyages to South America around the year C.E. 1000. No known animal farming occurred here.
- Mesoamerica: Agriculture from Central Mexico to northern South America also occurred from 10,000 years ago; it was also only plant based. Maize was a crop bred from teosinte grass, which has become one of the global staples. Beans, squash, and avocados were also grown in this region.
- The Andes: Starting around 8,000 years ago, local domesticated plants started with squash but later included potatoes, tomatoes, beans, and quinoa. Maize was brought down from Mesoamerica. The main farm animals were llamas, alpacas, and guinea pigs.
- Sub-Saharan Africa: This region went through a change 5,000 years ago called the Bantu expansion. The Bantu agriculturalists were established in West Central Africa and then expanded south and east. Native varieties of rice, yams, millet, and sorghum were grown across this area. Cattle were also domesticated here.
- Eastern North America: This region was the last major independent agriculture center, from 4,000 years ago. Squash and sunflower are the produce from this region that are most known today, though sumpweed and pitseed goosefoot were also farmed. Hunting was still the main source of animal products.
By 5,000 years ago, our species was well within the Neolithic Revolution. Agriculturalists spread to neighboring parts of the world with their domesticates, further expanding the use of this subsistence strategy. From this point, the human species changed from being primarily foragers to primarily agriculturalists with skilled control of their environments. The planet changed from mostly unaffected by human presence to being greatly transformed by humans. The revolution took millennia, but it was a true revolution as our species’ lifestyle was dramatically reshaped.
Cultural Effects of Agriculture
The worldwide adoption of agriculture altered the course of human culture and history forever. The core change in human culture due to agriculture is the move toward not moving: rather than live a nomadic lifestyle, farmers had to remain in one area to tend to their crops and livestock. The term for living bound to a certain location is sedentarism. This led to new aspects of life that were uncommon among foragers: the construction of permanent shelters and agricultural infrastructure, such as fields and irrigation, plus the development of storage technology, such as pottery, to preserve extra resources in case of future instability.
The high productivity of successful agriculture sparked further changes (Smith 2009). It is argued that since successful agriculture produced a much greater amount of food and other resources per unit of land compared to foraging, the population growth rate skyrocketed. The surplus of a bountiful harvest also provided insurance for harder times, reducing the risk of famine. Changes happened to society as well. With a few farming households producing enough food to feed many others, other people could focus on other tasks. So began specialization into different occupations such as craftspeople, traders, religious figures, and artists, spurring innovation in these areas as people could now devote time and effort toward specific skills. These interdependent people would settle an area together for convenience. The growth of these settlements led to urbanization, the founding of cities that became the foci of human interaction (Figure 13.24).
The formation of cities led to new issues that sparked the growth of further specializations, called institutions. These are cultural constructs that exist beyond the individual and have wide control over a population. Leadership of these cities became hierarchical with different levels of rank and control. The stratification of society increased social inequality between those with more or less power over others. Under leadership, people built impressive monumental architecture, such as pyramids and palaces, that embodied the wealth and power of these early cities. Alliances could unite cities, forming the earliest states. In several regions of the world, state organization expanded into empires, wide-ranging political entities that covered a variety of cultures.
Urbanization brought new challenges as well. The concentration of sedentary peoples was ideal for infectious diseases to thrive since they could jump from person to person and even from livestock to person (Armelagos, Brown, and Turner 2005). While successful agriculture provided a large surplus of food to thwart famine, the food produced offered less diverse food sources than foragers’ diets (Cohen and Armelagos 1984; Cohen and Crane-Kramer 2007). This shift in nutrition caused other diseases to flourish among those who adopted farming, such as dental cavities and malocclusion (the misalignment of teeth caused by soft, agricultural diets). The need to extract “wisdom teeth” or third molars seen in agricultural cultures today stems from this misalignment between the environment our ancestors adapted to and our lifestyles today.
As the new disease trends show, the adoption of agriculture and the ensuing cultural changes were not entirely positive. It is also important to note that this is not an absolutely linear progression of human culture from simple to complex. In many cases, empires have collapsed and, in some cases, cities dispersed to low-density bands that rejected institutions. However, a global trend has emerged since the adoption of agriculture, wherein population and social inequality have increased, leading to the massive and influential nation-states of today.
The rise of states in Europe has a direct impact on many of this book’s topics. Science started as a European cultural practice by the upper class that became a standardized way to study the world. Education became an institution to provide a standardized path toward producing and gaining knowledge. The scientific study of human diversity, embroiled in the race concept that still haunts us today, was connected to the European slave trade and colonialism.
Also starting in Europe, the Industrial Revolution of the 19th century turned cities into centers of mass manufacturing and spurred the rapid development of inventions (Figure 13.25). In the technologically interconnected world of today, human society has reached a new level of complexity with globalization. In this system, goods are mass-produced and consumed in different parts of the world, weakening the reliance on local farms and factories. The imbalanced relationship between consumers and producers of goods further increases economic inequality.
As states based on agriculture and industry keep exerting influence on humanity today, there are people, like the Hadzabe of Tanzania, who continue to live a lifestyle centered on foraging. Due to the overwhelming force that agricultural societies exert, foragers today have been marginalized to live in the least habitable parts of the world—the areas that are not conducive to farming, such as tropical rainforests, deserts, and the Arctic (Headland et al. 1989). Foragers can no longer live in the abundant environments that humans would have enjoyed before the Neolithic Revolution. Interactions with agriculturalists are typically imbalanced, with trade and other exchanges heavily favoring the larger group. One of anthropology’s important roles today is to intelligently and humanely manage equitable interactions between people of different backgrounds and levels of influence.
Special Topic: Indigenous Land Management
Insight into the lives of past modern humans has evolved as researchers revise previous theories and establish new connections with Indigenous knowledge holders.
The outdated view of foraging held that people lived off of the land without leaving an impact on the environment. Accompanying this idea was anthropologist Marshall Sahlins’s (1968) proposal that foragers were the “original affluent society” since they were meeting basic needs and achieving satisfaction with less work hours than agriculturalists and city-dwellers. This view countered an earlier idea that foragers were always on the brink of starvation. Sahlins’s theory took hold in the public eye as an attractive counterpoint to our busy contemporary lives in which we strive to meet our endless wants.
A fruitful type of study involving researchers collaborating with Indigenous experts has found that foragers did not just live off the land with minimal effort nor were they barely surviving in unchanging environments. Instead, they shaped the landscape to their needs using labor and strategies that were more subtle than what European colonizers and subsequent researchers were used to seeing. Research from two regions shows the latest developments in understanding Indigenous land management.
In British Columbia, Canada, the bridging of scientific and Indigenous perspectives has shown that the forests of the region are not untouched wilderness but, rather, have been crafted by Indigenous peoples thousands of years ago. Forest gardens adjacent to archaeological sites show higher plant diversity than unmanaged places even after 150 years (Armstrong et al. 2021). On the coast, 3,500-year-old archaeological sites are evidence of constructed clam gardens, according to Indigenous experts (Lepofsky et al. 2015). Another project, in consultation with Elders of the T’exelc (William Lakes First Nation) in British Columbia, introduced researchers to explanations of how forests were managed before the practice was disrupted by European colonialism (Copes-Gerbitz et al. 2021). Careful management of controlled fires reduced the density of the forest to favor plants such as raspberries and allow easier movement through the landscape.
Similarly, the study of landscapes in Australia, in consultation with Aboriginal Australians today, shows that areas previously considered wilderness by scientists were actually the result of controlling fauna and fires. The presence of grasslands with adjacent forests were purposely constructed to attract kangaroos for hunting (Gammage 2008). People also managed other animal and insect life, from emus to caterpillars. In Tasmania, a shift from productive grassland to wildfire-prone rainforest occurred after Aboriginal Australian land management was replaced by British colonial rule (Fletcher, Hall, and Alexander 2021). The site of Budj Bim of the Gunditjmara people has archaeological features of aquaculture, or the farming of fish, that date back 6,600 years (McNiven et al. 2012; McNiven et al. 2015). These examples show that Indigenous knowledge of how to manipulate the environment may be invaluable at the state level, such as by creating an Aboriginal ranger program to guide modern land management.
The Future of Humanity
A common question stemming from understanding human evolution is: What will the genetic and biological traits of our species be hundreds of thousands of years in the future? When faced with this question, people tend to think of directional selection. Maybe our braincases will be even larger, resembling the large-headed and small-bodied aliens of science fiction (Figure 13.26). Or, our hands could be specialized for interacting with our touch-based technology with less risk of repetitive injury. These ideas do not stand up to scrutiny. Since natural selection is based on adaptations that increase reproductive success, any directional change must be due to a higher rate of producing successful offspring compared to other alleles. Larger brains and more agile fingers would be convenient to possess, but they do not translate into an increase in the underlying allele frequencies.
Scientists are hesitant to professionally speculate on the unknowable, and we will never know what is in store for our species one thousand or one million years from now, but there are two trends in human evolution that may carry on into the future: increased genetic variation and a reduction in regional differences.
Rather than a directional change, genetic variation in our species could expand. Our technology can protect us from extreme environments and pathogens, even if our biological traits are not tuned to handle these stressors. The rapid pace of technological advancement means that biological adaptations will become less and less relevant to reproductive success, so nonbeneficial genetic traits will be more likely to remain in the gene pool. Biological anthropologist Jay T. Stock (2008) views environmental stress as needing to defeat two layers of protection before affecting our genetics. The first layer is our cultural adaptations. Our technology and knowledge can reduce pressure on one’s genotype to be “just right” to pass to the next generation. The second defense is our flexible physiology, such as our acclimatory responses. Only stressors not handled by these powerful responses would then cause natural selection on our alleles. These shields are already substantial, and cultural adaptations will only keep increasing in strength.
The increasing ability to travel far from one’s home region means that there will be a mixing of genetic variation on a global level in the future of our species. In recent centuries, gene flow of people around the world has increased, creating admixture in populations that had been separated for tens of thousands of years. For skin color, this means that populations all around the world could exhibit the whole range of skin colors, rather than the current pattern of decreasing melanin pigment farther from the equator. The same trend of intermixing would apply to all other traits, such as blood types. While our genetics will become more varied, the variation will be more intermixed instead of regionally isolated.
Our distant descendants will not likely be dextrous ultraintellectuals; more likely, they will be a highly variable and mobile species supported by novel cultural adaptations that make up for any inherited biological limitations. Technology may even enable the editing of DNA directly, changing these trends. With the uncertainty of our future, these are just the best-educated guesses for now. Our future is open and will be shaped little by little by the environment, our actions, and the actions of our descendants.
Summary
Modern Homo sapiens is the species that took the hominin lifestyle the furthest to become the only living member of that lineage. The largest factor that allowed us to persist while other hominins went extinct was likely our advanced ability to culturally adapt to a wide variety of environments. Our species, with its skeletal and behavioral traits, was well-suited to be generalist-specialists who successfully foraged across most of the world’s environments. The biological basis of this adaptation was our reorganized brain that facilitated innovation in cultural adaptations and intelligence for leveraging our social ties and finding ways to acquire resources from the environment. As the brain’s ability increased, it shaped the skull by reducing the evolutionary pressure to have large teeth and robust cranial bones to produce the modern Homo sapiens face.
Our ability to be generalist-specialists is seen in the geographical range that modern Homo sapiens covered in 300,000 years. In Africa, our species formed from multiregional gene flow that loosely connected archaic humans across the continent. People then expanded out to the rest of the continental Eurasia and even further to the Americas.
For most of our species’s existence, foraging was the general subsistence strategy within which people specialized to culturally adapt to their local environment. With omnivorousness and mobility, people found ways to extract and process resources, shaping the environment in return. When resource uncertainty hit the species, people around the world focused on agriculture to have a firmer control of sustenance. The new strategy shifted human history toward exponential growth and innovation, leading to our high dependence on cultural adaptations today.
While a cohesive image of our species has formed in recent years, there is still much to learn about our past. The work of many driven researchers shows that there are amazing new discoveries made all the time that refine our knowledge of human evolution. Technological innovations such as DNA analysis enable scientists to approach lingering questions from new angles. The answers we get allow us to ask even more insightful questions that will lead us to the next revelation. Like the pink limestone strata at Jebel Irhoud, previous effort has taken us so far and you are now ready to see what the next layer of discovery holds.
Hominin Species Summary
|
Hominin |
Modern Homo sapiens |
|
Dates |
315,000 years ago to present |
|
Region(s) |
Starting in Africa, then expanding around the world |
|
Famous discoveries |
Cro-Magnon individuals, discovered 1868 in Dordogne, France. Otzi the Ice Man, discovered 1991 in the Alps between Austria and Italy. Kennewick man, discovered 1996 in Washington state. |
|
Brain size |
1400 cc average |
|
Dentition |
Extremely small with short cusps. |
|
Cranial features |
An extremely globular brain case and gracile features throughout the cranium. The mandibular symphysis forms a chin at the anterior-most point. |
|
Postcranial features |
Gracile skeleton adapted for efficient bipedal locomotion at the expense of the muscular strength of most other large primates. |
|
Culture |
Extremely extensive and varied culture with many spoken and written languages. Art is ubiquitous. Technology is broad in complexity and impact on the environment. |
|
Other |
The only living hominin. Chimpanzees and bonobos are the closest living relatives. |
Review Questions
- What are the skeletal and behavioral traits that define modern Homo sapiens? What are the evolutionary explanations for its presence?
- What are some creative ways that researchers have learned about the past by studying fossils and artifacts?
- How do the discoveries mentioned in “First Africa, Then the World” fit the Assimilation model?
- What is foraging? What adaptations do we have for this subsistence strategy? Could you train to be a skilled forager?
- What are aspects of your life that come from dependence on agriculture and its cultural effects? Where did the ingredients of your favorite foods originate from?
Key Terms
African multiregionalism: The idea that modern Homo sapiens evolved as a complex web of small regional populations with sporadic gene flow among them.
Agriculture: The mass production of resources through farming and domestication.
Aquaculture: The farming of fish using techniques such as trapping, channels, and artificial ponds.
Assimilation hypothesis: Current theory of modern human origins stating that the species evolved first in Africa and interbred with archaic humans of Europe and Asia.
Atlatl: A handheld spear thrower that increased the force of thrown projectiles.
Band: A small group of people living together as foragers.
Beringia: Ancient landmass that connected Siberia and Alaska. The ancestors of Indigenous Americans would have crossed this area to reach the Americas.
Carrying capacity: The amount of organisms that an environment can reliably support.
Coastal Route model: Theory that the first Paleoindians crossed to the Americas by following the southern coast of Beringia.
Early Modern Homo sapiens, Early Anatomically Modern Human: Terms used to refer to transitional fossils between archaic and modern Homo sapiens that have a mosaic of traits. Humans like ourselves, who mostly lack archaic traits, are referred to as Late Modern Homo sapiens and simply Anatomically Modern Humans.
Egalitarian: Human organization without strict ranks. Foraging societies tend to be more egalitarian than those based on other subsistence strategies.
Foraging: Lifestyle consisting of frequent movement through the landscape and acquiring resources with minimal storage capacity.
Generalist-specialist niche: The ability to survive in a variety of environments by developing local expertise. Evolution toward this niche may have been what allowed modern Homo sapiens to expand past the geographical range of other human species.
Globalization: A recent increase in the interconnectedness and interdependence of people that is facilitated with long-distance networks.
Globular: Having a rounded appearance. Increased globularity of the braincase is a trait of modern Homo sapiens.
Gracile: Having a smooth and slender quality; the opposite of robust.
Holocene: The epoch of the Cenozoic Era starting around 12,000 years ago and lasting arguably through the present.
Ice-Free Corridor model: Theory that the first Native Americans crossed to the Americas through a passage between glaciers.
Institutions: Long-lasting and influential cultural constructs. Examples include government, organized religion, academia, and the economy.
Last Glacial Maximum: The time 23,000 years ago when the most recent ice age was the most intense.
Later Stone Age: Time period following the Middle Stone Age with a diversification in tool types, starting around 50,000 years ago.
Levant: The eastern coast of the Mediterranean. The site of early modern human expansion from Africa and later one of the centers of agriculture.
Megafauna: Large ancient animals that may have been hunted to extinction by people around the world.
Mental eminence: The chin on the mandible of modern H. sapiens. One of the defining traits of our species.
Microlith: Small stone tool found in the Later Stone Age; also called a bladelet.
Middle Stone Age: Time period known for Mousterian lithics that connects African archaic to modern Homo sapiens.
Monumental architecture: Large and labor-intensive constructions that signify the power of the elite in a sedentary society. A common type is the pyramid, a raised crafted structure topped with a point or platform.
Mosaic: Composed from a mix or composite of traits.
Neolithic Revolution: Time of rapid change to human cultures due to the invention of agriculture, starting around 12,000 years ago.
Ochre: Iron-based mineral pigment that can be a variety of yellows, reds, and browns. Used by modern human cultures worldwide since at least 80,000 years ago.
Sahul: Ancient landmass connecting New Guinea and Australia.
Sedentarism: Lifestyle based on having a stable home area; the opposite of nomadism.
Southern Dispersal model: Theory that modern H. sapiens expanded from East Africa by crossing the Red Sea and following the coast east across Asia.
Subsistence strategy: The method an organism uses to find nourishment and other resources.
Sunda: Ancient Asian landmass that incorporated modern Southeast Asia.
Supraorbital torus: The bony brow ridge across the top of the eye orbits on many hominin crania.
Upper Paleolithic: Time period considered synonymous with the Later Stone Age.
Urbanization: The increase of population density as people settled together in cities.
Wallacea: Archipelago southeast of Sunda with different biodiversity than Asia.
Younger Dryas: The rapid change in global climate—notably a cooling of the Northern Hemisphere—13,000 years ago.
For Further Exploration
Websites
First-person virtual tour of Lascaux cave with annotated cave art: Ministère de la Culture and Musée d’Archéologie Nationale. “Visit the cave” Lascaux website.
Online anthropology magazine articles related to paleoanthropology and human evolution: SAPIENS. “Evolution.” SAPIENS website.
Various presentations of information about hominin evolution: Smithsonian Institution. “What does it mean to be human?” Smithsonian National Museum of Natural History website.
Magazine-style articles on archaeology and paleoanthropology: ThoughtCo. “Archaeology.” ThoughtCo. Website.
Database of comparisons across hominins and primates: University of California, San Diego. “MOCA Domains.” Center for Academic Research & Training in Anthropogeny website.
Books
Engaging book that covers human-made changes to the environment with industrialization and globalization: Kolbert, Elizabeth. 2014. The Sixth Extinction: An Unnatural History. New York: Bloomsbury.
Overview of what human life was like among the environmental shifts of the Ice Age: Woodward, Jamie. 2014. The Ice Age: A Very Short Introduction. Oxford: OUP Press.
Articles
Recent review paper about the current state of paleoanthropology research: Stringer, C. 2016. “The Origin and Evolution of Homo sapiens.” Philosophical Transactions of the Royal Society B 371 (1698).
Overview of the history of American paleoanthropology and the many debates that have occurred over the years: Trinkaus, E. 2018. “One Hundred Years of Paleoanthropology: An American Perspective.” American Journal of Physical Anthropology 165 (4): 638–651.
Amazing magazine article that synthesizes hominin evolution and why it is important to study this subject: Wheelwright, Jeff. 2015. “Days of Dysevolution.” Discover 36 (4): 33–39.
Fascinating research on Ötzi, a mummy from 5,000 years ago: Wierer, Ursula, Simona Arrighi, Stefano Bertola, Günther Kaufmann, Benno Baumgarten, Annaluisa Pedrotti, Patrizia Pernter, and Jacques Pelegrin. 2018. “The Iceman’s Lithic Toolkit: Raw Material, Technology, Typology and Use.” PLOS One 13 (6): e0198292. https://doi.org/10.1371/journal.pone.0198292.
Documentaries
PBS NOVA series covering the expansion of modern Homo sapiens and interbreeding with archaic humans: Brown, Nicholas, dir. 2015. First Peoples. Edmonton: Wall to Wall Television. Amazon Prime Video.
PBS NOVA special featuring the footprints found in White Sands National Park: Falk, Bella, dir. 2016. Ice Age Footprints. Boston: Windfall Films. https://www.pbs.org/wgbh/nova/video/ice-age-footprints/.
PBS NOVA special about how modern humans evolved adaptations to different environments. Shows how present-day people live around the world: Thompson, Niobe, dir. 2016. Great Human Odyssey. Edmonton: Clearwater Documentary. https://www.pbs.org/wgbh/nova/evolution/great-human-odyssey.html.
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Acknowledgments
I could not have undertaken this project without the help of many who got me to where I am today. I extend sincere thank yous to the many colleagues and former students who have inspired me to keep learning and talking about anthropology. Thank you also to all who are involved in this textbook project. The anonymous reviewers truly sparked improvements to the chapter. Lastly, the staff of Starbucks #5772 also contributed immensely to this text.
Keith Chan, Ph.D., Grossmont-Cuyamaca Community College District and MiraCosta College
This chapter is a revision from "Chapter 12: Modern Homo sapiens” by Keith Chan. In Explorations: An Open Invitation to Biological Anthropology, first edition, edited by Beth Shook, Katie Nelson, Kelsie Aguilera, and Lara Braff, which is licensed under CC BY-NC 4.0.
Learning Objectives
- Identify the skeletal and behavioral traits that represent modern Homo sapiens.
- Critically evaluate different types of evidence for the origin of our species in Africa and our expansion around the world.
- Understand how the human lifestyle changed when people transitioned from foraging to agriculture.
- Hypothesize how human evolutionary trends may continue into the future.
The walls of a pink limestone cave in the hillside of Jebel Irhoud jutted out of the otherwise barren landscape of the Moroccan desert (Figure 13.1). Miners had excavated the cave in the 1960s, revealing some fossils. In 2007, a re-excavation of the site became a momentous occasion for science. A fossil cranium unearthed by a team of researchers was barely visible to the untrained eye. Just the fossil’s robust brows were peering out of the rock. This research team from the Max Planck Institute for Evolutionary Anthropology was the latest to explore the ancient human presence in this part of North Africa after a find by miners in 1960. Excavating near the first discovery, the researchers wanted to learn more about how Homo sapiens lived far from East Africa, where we thought our species originated.
The scientists were surprised when they analyzed the cranium, named Irhoud 10, and other fossils. Statistical comparisons with other human crania concluded that the Irhoud face shapes were typical of recent modern humans while the braincases matched ancient modern humans. Based on the findings of other scientists, the team expected these modern Homo sapiens fossils to be around 200,000 years old. Instead, dating revealed that the cranium had been buried for around 315,000 years.
Together, the modern-looking facial dimensions and the older date reshaped the interpretation of our species: modern Homo sapiens. Some key evolutionary changes from the archaic Homo sapiens (described in Chapter 11) to our species today happened 100,000 years earlier than we had thought and across the vast African continent rather than concentrated in its eastern region.
This revelation in the study of modern Homo sapiens is just one of the latest in this continually advancing area of biological anthropology. Researchers today are still discovering amazing fossils and ingenious ways to collect data and test hypotheses about our past. Through the collective work of many scientists, we are building an overall theory of modern human origins.
Defining Modernity
What defines modern Homo sapiens when compared to archaic Homo sapiens? Modern humans, like you and me, have a set of derived traits that are not seen in archaic humans or any other hominin. As with other transitions in hominin evolution, such as increasing brain size and bipedal ability, modern traits do not appear fully formed or all at once. In other words, the first modern Homo sapiens was not just born one day from archaic parents. The traits common to modern Homo sapiens appeared in a mosaic manner: gradually and out of sync with one another. There are two areas to consider when tracking the complex evolution of modern human traits. One is the physical change in the skeleton. The other is behavior inferred from the size and shape of the cranium and material culture evidence.
Skeletal Traits
The skeleton of modern Homo sapiens is less robust than that of archaic Homo sapiens. In other words, the modern skeleton is gracile, meaning that the structures are thinner and smoother. Differences related to gracility in the cranium are seen in the braincase, the face, and the mandible. There are also broad differences in the rest of the skeleton.
Cranial Traits
Several elements of the braincase differ between modern and archaic Homo sapiens. Overall, the shape is much rounder, or more globular, on a modern skull (Lieberman, McBratney, and Krovitz 2002; Neubauer, Hublin, and Gunz 2018; Pearson 2008; Figure 13.2). You can feel the globularity of your own modern human skull. Feel the height of your forehead with the palm of your hand. Viewed from the side, the tall vertical forehead of a modern Homo sapiens stands out when compared to the sloping archaic version. This is because the frontal lobe of the modern human brain is larger than the one in archaic humans, and the skull has to accommodate the expansion. The vertical forehead reduces a trait that is common to all other hominins: the brow ridge or supraorbital torus. The parietal lobes of the brain and the matching parietal bones on either side of the skull both bulge outward more in modern humans. At the back of the skull, the archaic occipital bun is no longer present. Instead, the occipital region of the modern human cranium has a derived tall and smooth curve, again reflecting the globular brain inside.
The trend of shrinking face size across hominins reaches its extreme with our species as well. The facial bones of a modern Homo sapiens are extremely gracile compared to all other hominins (Lieberman, McBratney, and Krovitz 2002). Continuing a trend in hominin evolution, technological innovations kept reducing the importance of teeth in reproductive success (Lucas 2007). As natural selection favored smaller and smaller teeth, the surrounding bone holding these teeth also shrank.
Related to smaller teeth, the mandible is also gracile in modern humans when compared to archaic humans and other hominins. Interestingly, our mandibles have pulled back so far from the prognathism of earlier hominins that we gained an extra structure at the most anterior point, called the mental eminence. You know this structure as the chin. At the skeletal level, it resembles an upside-down “T” at the centerline of the mandible (Pearson 2008). Looking back at archaic humans, you will see that they all lack a chin. Instead, their mandibles curve straight back without a forward point. What is the chin for and how did it develop? Flora Gröning and colleagues (2011) found evidence of the chin’s importance by simulating physical forces on computer models of different mandible shapes. Their results showed that the chin acts as structural support to withstand strain on the otherwise gracile mandible.
Postcranial Gracility
The rest of the modern human skeleton is also more gracile than its archaic counterpart. The differences are clear when comparing a modern Homo sapiens with a cold-adapted Neanderthal (Sawyer and Maley 2005), but the trends are still present when comparing modern and archaic humans within Africa (Pearson 2000). Overall, a modern Homo sapiens postcranial skeleton has thinner cortical bone, smoother features, and more slender shapes when compared to archaic Homo sapiens (Figure 13.3). Comparing whole skeletons, modern humans have longer limb proportions relative to the length and width of the torso, giving us lankier outlines.
Why is our skeleton so gracile compared to those of other hominins? Natural selection can drive the gracilization of skeletons in several ways (Lieberman 2015). A slender frame is believed to be adapted for the efficient long-distance running ability that started with Homo erectus. Furthermore, it is argued that slenderness is a genetic adaptation for cooling an active body in hotter climates, which aligns with the ample evidence that Africa was the home continent of our species.
Behavioral Modernity
Aside from physical differences in the skeleton, researchers have also uncovered evidence of behavioral changes associated with increased cultural complexity from archaic to modern humans. How did cultural complexity develop? Two investigations into this question are archaeology and the analysis of reconstructed brains.
Archaeology tells us much about the behavioral complexity of past humans by interpreting the significance of material culture. In terms of advanced culture, items created with an artistic flair, or as decoration, speak of abstract thought processes (Figure 13.4). The demonstration of difficult artistic techniques and technological complexity hints at social learning and cooperation as well. According to paleoanthropologist John Shea (2011), one way to track the complexity of past behavior through artifacts is by measuring the variety of tools found together. The more types of tools constructed with different techniques and for different purposes, the more modern the behavior. Researchers are still working on an archaeological way to measure cultural complexity that is useful across time and place.
The interpretation of brain anatomy is another promising approach to studying the evolution of human behavior. When looking at investigations on this topic in modern Homo sapiens brains, researchers found a weak association between brain size and test-measured intelligence (Pietschnig et al. 2015). Additionally, they found no association between intelligence and biological sex. These findings mean that there are more significant factors that affect tested intelligence than just brain size. Since the sheer size of the brain is not useful for weighing intelligence within a species, paleoanthropologists are instead investigating the differences in certain brain structures. The differences in organization between modern Homo sapiens brains and archaic Homo sapiens brains may reflect different cognitive priorities that account for modern human culture. As with the archaeological approach, new discoveries will refine what we know about the human brain and apply that knowledge to studying the distant past.
Taken together, the cognitive abilities in modern humans may have translated into an adept use of tools to enhance survival. Researchers Patrick Roberts and Brian A. Stewart (2018) call this concept the generalist-specialist niche: our species is an expert at living in a wide array of environments, with populations culturally specializing in their own particular surroundings. The next section tracks how far around the world these skeletal and behavioral traits have taken us.
First Africa, Then the World
What enabled modern Homo sapiens to expand its range further in 300,000 years than Homo erectus did in 1.5 million years? The key is the set of derived biological traits from the last section. It is theorized that the gracile frame and neurological anatomy allowed modern humans to survive and even flourish in the vastly different environments they encountered. Based on multiple types of evidence, the source of all of these modern humans was Africa. Instead of originating from just one location, evidence shows that modern Homo sapiens evolution occurred in a complex gene flow network across Africa, a concept called African multiregionalism (Scerri et al. 2018).
This section traces the origin of modern Homo sapiens and the massive expansion of our species across all of the continents (except Antarctica) by 12,000 years ago. While modern Homo sapiens first shared geography with archaic humans, modern humans eventually spread into lands where no human had gone before. Figure 13.5 shows the broad routes that our species took expanding around the world. I encourage you to make your own timeline with the dates in this part to see the overall trends.
Modern Homo sapiens Biology and Culture in Africa
We start with the ample fossil evidence supporting the theory that modern humans originated in Africa during the Middle Pleistocene, having evolved from African archaic Homo sapiens. The earliest dated fossils considered to be modern actually have a mosaic of archaic and modern traits, showing the complex changes from one type to the other. Experts have various names for these transitional fossils, such as Early Modern Homo sapiens or Early Anatomically Modern Humans. However they are labeled, the presence of some modern traits means that they illustrate the origin of the modern type. Three particularly informative sites with fossils of the earliest modern Homo sapiens are Jebel Irhoud, Omo, and Herto.
Recall from the start of the chapter that the most recent finds at Jebel Irhoud are now the oldest dated fossils that exhibit some facial traits of modern Homo sapiens. Besides Irhoud 10, the cranium that was dated to 315,000 years ago (Hublin et al. 2017; Richter et al. 2017), there were other fossils found in the same deposit that we now know are from the same time period. In total there are at least five individuals, representing life stages from childhood to adulthood. These fossils form an image of high variation in skeletal traits. For example, the skull named Irhoud 1 has a primitive brow ridge, while Irhoud 2 and Irhoud 10 do not (Figure 13.6). The braincases are lower than what is seen in the modern humans of today but higher than in archaic Homo sapiens. The teeth also have a mix of archaic and modern traits that defy clear categorization into either group.
Research separated by nearly four decades uncovered fossils and artifacts from the Kibish Formation in the Lower Omo Valley in Ethiopia. These Omo Kibish hominins were represented by braincases and fragmented postcranial bones of three individuals found kilometers apart, dating back to around 233,000 years ago (Day 1969; McDougall, Brown, and Fleagle 2005; Vidal et al. 2022). One interesting finding was the variation in braincase size between the two more-complete specimens: while the individual named Omo I had a more globular dome, Omo II had an archaic-style long and low cranium.
Also in Ethiopia, a team led by Tim White (2003) excavated numerous fossils at Herto. There were fossilized crania of two adults and a child, along with fragments of more individuals. The dates ranged between 160,000 and 154,000 years ago. The skeletal traits and stone-tool assemblage were both intermediate between the archaic and modern types. Features reminiscent of modern humans included a tall braincase and thinner zygomatic (cheek) bones than those of archaic humans (Figure 13.7). Still, some archaic traits persisted in the Herto fossils, such as the supraorbital tori. Statistical analysis by other research teams concluded that at least some cranial measurements fit just within the modern human range (McCarthy and Lucas 2014), favoring categorization with our own species.
The timeline of material culture suggests a long period of relying on similar tools before a noticeable diversification of artifacts types. Researchers label the time of stable technology shared with archaic types the Middle Stone Age, while the subsequent time of diversification in material culture is called the Later Stone Age.
In the Middle Stone Age, the sites of Jebel Irhoud, Omo, and Herto all bore tools of the same flaked style as archaic assemblages, even though they were separated by almost 150,000 years. The consistency in technology may be evidence that behavioral modernity was not so developed. No clear signs of art dating back this far have been found either. Other hypotheses not related to behavioral modernity could explain these observations. The tool set may have been suitable for thriving in Africa without further innovation. Maybe works of art from that time were made with media that deteriorated or perhaps such art was removed by later humans.
Evidence of what Homo sapiens did in Africa from the end of the Middle Stone Age to the Later Stone Age is concentrated in South African cave sites that reveal the complexity of human behavior at the time. For example, Blombos Cave, located along the present shore of the Cape of Africa facing the Indian Ocean, is notable for having a wide variety of artifacts. The material culture shows that toolmaking and artistry were more complex than previously thought for the Middle Stone Age. In a layer dated to 100,000 years ago, researchers found two intact ochre-processing kits made of abalone shells and grinding stones (Henshilwood et al. 2011). Marine snail shell beads from 75,000 years ago were also excavated (Figure 13.8; d’Errico et al. 2005). Together, the evidence shows that the Middle Stone Age occupation at Blombos Cave incorporated resources from a variety of local environments into their culture, from caves (ochre), open land (animal bones and fat), and the sea (abalone and snail shells). This complexity shows a deep knowledge of the region’s resources and their use—not just for survival but also for symbolic purposes.
On the eastern coast of South Africa, Border Cave shows new African cultural developments at the start of the Later Stone Age. Paola Villa and colleagues (2012) identified several changes in technology around 43,000 years ago. Stone-tool production transitioned from a slower process to one that was faster and made many microliths, small and precise stone tools. Changes in decorations were also found across the Later Stone Age transition. Beads were made from a new resource: fragments of ostrich eggs shaped into circular forms resembling present-day breakfast cereal O’s (d’Errico et al. 2012). These beads show a higher level of altering one’s own surroundings and a move from the natural to the abstract in terms of design.
Expansion into the Middle East and Asia
While modern Homo sapiens lived across Africa, some members eventually left the continent. These pioneers could have used two connections to the Middle East or West Asia. From North Africa, they could have crossed the Sinai Peninsula and moved north to the Levant, or eastern Mediterranean. Finds in that region show an early modern human presence. Other finds support the Southern Dispersal model, with a crossing from East Africa to the southern Arabian Peninsula through the Straits of Bab-el-Mandeb. It is tempting to think of one momentous event in which people stepped off Africa and into the Middle East, never to look back. In reality, there were likely multiple waves of movement producing gene flow back and forth across these regions as the overall range pushed east. The expanding modern human population could have thrived by using resources along the southern coast of the Arabian Peninsula to South Asia, with side routes moving north along rivers. The maximum range of the species then grew across Asia.
Modern Homo sapiens in the Middle East
Geographically, the Middle East is the ideal place for the African modern Homo sapiens population to inhabit upon expanding out of their home continent. In the Eastern Mediterranean coast of the Levant, there is a wealth of skeletal and material culture linked to modern Homo sapiens. Recent discoveries from Saudi Arabia further add to our view of human life just beyond Africa.
The Caves of Mount Carmel in present-day Israel have preserved skeletal remains and artifacts of modern Homo sapiens, the first-known group living outside Africa. The skeletal presence at Misliya Cave is represented by just part of the left upper jaw of one individual, but it is notable for being dated to a very early time, between 194,000 and 177,000 years ago (Hershkovitz et al. 2018). Later, from 120,000 to 90,000 years ago, fossils of multiple individuals across life stages were found in the caves of Es-Skhul and Qafzeh (Shea and Bar-Yosef 2005). The skeletons had many modern Homo sapiens traits, such as globular crania and more gracile postcranial bones when compared to Neanderthals. Still, there were some archaic traits. For example, the adult male Skhul V also possessed what researchers Daniel Lieberman, Osbjorn Pearson, and Kenneth Mowbray (2000) called marked or clear occipital bunning. Also, compared to later modern humans, the Mount Carmel people were more robust. Skhul V had a particularly impressive brow ridge that was short in height but sharply jutted forward above the eyes (Figure 13.9). The high level of preservation is due to the intentional burial of some of these people. Besides skeletal material, there are signs of artistic or symbolic behavior. For example, the adult male Skhul V had a boar’s jaw on his chest. Similarly, Qafzeh 11, a juvenile with healed cranial trauma, had an impressive deer antler rack placed over his torso (Figure 13.10; Coqueugniot et al. 2014). Perforated seashells colored with ochre, mineral-based pigment, were also found in Qafzeh (Bar-Yosef Mayer, Vandermeersch, and Bar-Yosef 2009).
One remaining question is, what happened to the modern humans of the Levant after 90,000 years ago? Another site attributed to our species did not appear in the region until 47,000 years ago. Competition with Neanderthals may have accounted for the disappearance of modern human occupation since the Neanderthal presence in the Levant lasted longer than the dates of the early modern Homo sapiens. John Shea and Ofer Bar-Yosef (2005) hypothesized that the Mount Carmel modern humans were an initial expansion from Africa that failed. Perhaps they could not succeed due to competition with the Neanderthals who had been there longer and had both cultural and biological adaptations to that environment.
Modern Homo sapiens of China
A long history of paleoanthropology in China has found ample evidence of modern human presence. Four notable sites are the caves at Fuyan, Liujiang, Tianyuan, and Zhoukoudian. In the distant past, these caves would have been at least seasonal shelters that unintentionally preserved evidence of human presence for modern researchers to discover.
At Fuyan Cave in Southern China, paleoanthropologists found 47 adult teeth associated with cave formations dated to between 120,000 and 80,000 years ago (Liu et al. 2015). It is currently the oldest-known modern human site in China, though other researchers question the validity of the date range (Michel et al. 2016). The teeth have the small size and gracile features of modern Homo sapiens dentition.
The fossil Liujiang (or Liukiang) hominin (67,000 years ago) has derived traits that classified it as a modern Homo sapiens, though primitive archaic traits were also present. In the skull, which was found nearly complete, the Liujiang hominin had a taller forehead than archaic Homo sapiens but also had an enlarged occipital region (Figure 13.11; Brown 1999; Wu et al. 2008). Other parts of the skeleton also had a mix of modern and archaic traits: for example, the femur fragments suggested a slender length but with thick bone walls (Woo 1959).
Another Chinese site to describe here is the one that has been studied the longest. In the Zhoukoudian Cave system (Figure 13.12), where Homo erectus and archaic Homo sapiens have also been found, there were three crania of modern Homo sapiens. These crania, which date to between 34,000 and 10,000 years ago, were all more globular than those of archaic humans but still lower and longer than those of later modern humans (Brown 1999; Harvati 2009). When compared to one another, the crania showed significant differences from one another. Comparison of cranial measurements to other populations past and present found no connection with modern East Asians, again showing that human variation was very different from what we see today.
Crossing to Australia
Expansion of the first modern human Asians, still following the coast, eventually entered an area that researchers call Sunda before continuing on to modern Australia. Sunda was a landmass made up of the modern-day Malay Peninsula, Sumatra, Java, and Borneo. Lowered sea levels connected these places with land bridges, making them easier to traverse. Proceeding past Sunda meant navigating Wallacea, the archipelago that includes the Indonesian islands east of Borneo. In the distant past, there were many megafauna, large animals that migrating humans would have used for food and materials (such as utilizing animals’ hides and bones). Further southeast was another landmass called Sahul, which included New Guinea and Australia as one contiguous continent. Based on fossil evidence, this land had never seen hominins or any other primates before modern Homo sapiens arrived. Sites along this path offer clues about how our species handled the new environment to live successfully as foragers.
The skeletal remains at Lake Mungo, land traditionally owned by Mutthi Mutthi, Ngiampaa, and Paakantji peoples, are the oldest known in the continent. The now-dry lake was one of a series located along the southern coast of Australia in New South Wales, far from where the first people entered from the north (Barbetti and Allen 1972; Bowler et al. 1970). Two individuals dating to around 40,000 years ago show signs of artistic and symbolic behavior, including intentional burial. The bones of Lake Mungo 1 (LM1), an adult female, were crushed repeatedly, colored with red ochre, and cremated (Bowler et al. 1970). Lake Mungo 3 (LM3), a tall, older male with a gracile cranium but robust postcranial bones, had his fingers interlocked over his pelvic region (Brown 2000).
Kow Swamp, within traditional Yorta Yorta land also in southern Australia, contained human crania that looked distinctly different from the ones at Lake Mungo (Durband 2014; Thorne and Macumber 1972). The crania, dated between 9,000 and 20,000 years ago, had extremely robust brow ridges and thick bone walls, but these were paired with globular features on the braincase (Figure 13.13).
While no fossil humans have been found at the Madjedbebe rock shelter in the North Territory of Australia, more than 10,000 artifacts found there show both behavioral modernity and variability (Clarkson et al. 2017). They include a diverse array of stone tools and different shades of ochre for rock art, including mica-based reflective pigment (similar to glitter). These impressive artifacts are as far back as 56,000 years old, providing the date for the earliest-known presence of humans in Australia.
From the Levant to Europe
The first modern human expansion into Europe occurred after other members of our species settled in East Asia and Australia. As the evidence from the Levant suggests, modern human movement to Europe may have been hampered by the presence of Neanderthals. It is suggested that another obstacle was the colder climate, which was incompatible with the biology of modern Homo sapiens from Africa, as they were adapted to high temperatures and ultraviolet radiation. Still, by 40,000 years ago, modern Homo sapiens had a detectable presence. This time was also the start of the Later Stone Age or Upper Paleolithic, when there was an expansion in cultural complexity. There is a wealth of evidence from this region due to a Western bias in research, the proximity of these findings to Western scientific institutions, and the desire of Western scientists to explore their own past.
In Romania, the site of Peștera cu Oase (Cave of Bones) had the oldest-known remains of modern Homo sapiens in Europe, dated to around 40,000 years ago (Trinkaus et al. 2003a). Among the bones and teeth of many animals were the fragmented cranium of one person and the mandible of another (the two bones did not fit each other). Both bones have modern human traits similar to the fossils from the Middle East, but they also had Neanderthal traits. Oase 1, the mandible, had a mental eminence but also extremely large molars (Trinkaus et al. 2003b). This mandible has yielded DNA that surprisingly is equally similar to DNA from present-day Europeans and Asians (Fu et al. 2015). This means that Oase 1 was not the direct ancestor of modern Europeans. The Oase 2 cranium has the derived traits of reduced brow ridges along with archaic wide zygomatic cheekbones and an occipital bun (Figure 13.14; Rougier et al. 2007).
Dating to around 26,000 years ago, Předmostí near Přerov in the Czech Republic was a site where people buried over 30 individuals along with many artifacts. Eighteen individuals were found in one mass burial area, a few covered by the scapulae of woolly mammoths (Germonpré, Lázničková-Galetová, and Sablin 2012). The Předmostí crania were more globular than those of archaic humans but tended to be longer and lower than in later modern humans (Figure 13.15; Velemínská et al. 2008). The height of the face was in line with modern residents of Central Europe. There was also skeletal evidence of dog domestication, such as the presence of dog skulls with shorter snouts than in wild wolves (Germonpré, Lázničková-Galetová, and Sablin et al. 2012). In total, Předmostí could have been a settlement dependent on mammoths for subsistence and the artificial selection of early domesticated dogs.
The sequence of modern Homo sapiens technological change in the Later Stone Age has been thoroughly dated and labeled by researchers working in Europe. Among them, the Gravettian tradition of 33,000 years to 21,000 years ago is associated with most of the known curvy female figurines, often assumed to be “Venus” figures. Hunting technology also advanced in this time with the first known boomerang, atlatl (spear thrower), and archery. The Magdalenian tradition spread from 17,000 to 12,000 years ago. This culture further expanded on fine bone tool work, including barbed spearheads and fishhooks (Figure 13.16).
Among the many European sites dating to the Later Stone Age, the famous cave art sites deserve mention. Chauvet-Pont-d'Arc Cave in southern France dates to separate Aurignacian occupations 31,000 years ago and 26,000 years ago. Over a hundred art pieces representing 13 animal species are preserved, from commonly depicted deer and horses to rarer rhinos and owls. Another French cave with art is Lascaux, which is several thousand years younger at 17,000 years ago in the Magdalenian period. At this site, there are over 6,000 painted figures on the walls and ceiling (Figure 13.17). Scaffolding and lighting must have been used to make the paintings on the walls and ceiling deep in the cave. Overall, visiting Lascaux as a contemporary must have been an awesome experience: trekking deeper in the cave lit only by torches giving glimpses of animals all around as mysterious sounds echoed through the galleries.
Special Topic: Cannibalism and Culture - Mortuary Practices in Modern Homo sapiens
Within a 2017 publication in the Journal of Archaeological Method and Theory, Saladié and Rodríguez-Hidalgo bring light to traces of early cannibalism in western Eurasia, arguing that context-specific cannibalistic practices were present throughout the Pleistocene and increased notably from the end of the Upper Palaeolithic and onward (Saladié & Rodriguez-Hidalgo, 2017). While early hominins and Neandertals are recognized in this research, the authors highlight the presence of these mortuary practices in a cluster of Homo Sapien sites. More recent research uncovers similar findings that back these claims as well, where human bones in Herto Ethiopia, Maszycka Cave Poland, and Gough’s Cave in the United Kingdom show anthropogenic defleshing and other modifications which have been interpreted as cannibalism (Pobiner, Et al. 2023). These findings suggest that cannibalistic behaviours formed a recurring aspect of modern human behaviour in certain ecological and cultural contexts.
A significant example comes from the Neolithic levels of Fontbrégua Cave in southeastern France, where Paola Villa and colleagues compared clusters of human bones with the remains of wild and domestic animals from the same sediments. The study found that human bodies were butchered, processed, and most likely eaten in a way that parallels animal carcass treatment, including the placement and timing of cut marks, dismemberment sequences, and perimortem fractures to open marrow cavities (Villa, Et al. 1986). As the assemblage comes from a primary depositional context with pristine preservation and careful excavation, the authors suggest that cannibalism is the only satisfactory explanation for the pattern of cut marks and breakage seen on the human bones.
More recent work has furthered this hypothesis for Late Upper Palaeolithic Homo sapiens, especially in Magdalenian contexts. In a 2023 study, researchers combined archeological and genetic evidence from fifty-nine Magdalenian sites, concluding that this specific culture shows an unusually high frequency of cannibalistic cases compared to earlier and later hominin groups; so much so that they identify “primary burial and cannibalism” as the two main mortuary expressions (Marsh & Bello, 2023). Additionally, new analyses from Maszycka Cave in Poland have described cut and broken human bones in patterns consistent with human consumption, reinforcing this cannibalism hypothesis (Marginedas & Saladié, 2025). Together, these studies suggest that for some Magdalenian groups, mortuary cannibalism was a habitual way of disposing of the dead, not just a one-off crisis response. At the same time, researchers emphasize that not every modified skeleton indicates blatant consumption of the dead and that ritual or symbolic perspectives must also be considered. Previously noted in chapter eleven, Ullrich’s survey of European mortuary practices presents frequent manipulations of corpses from the Palaeolithic through the Hallstatt period. Said manipulations include cut marks, dismemberment, skull fracturing, and marrow extraction (Ullrich, 2005, p. 258), which Ullrich interprets as cannibalistic rites embedded in cult ceremonies rather than everyday subsistence. In the author’s view, some Palaeolithic groups may have believed that consuming members of their community allowed them to take on the strengths, abilities, or even mental aspects of their dead member; the act of cannibalism may have functioned as a form of appropriating physical and mental powers rather than simply obtaining calories. With that, Neolithic assemblages show how careful taphonomic work can distinguish cuts linked to interpersonal violence from those associated with systemic butchery (Marginedas & Saladié, 2025). The findings seek to highlight that some Homo sapiens populations combined ritual, mortuary, and nutritional motives when processing human remains.
These past and contemporary findings are significant for future anthropology students as they shed light on biological anthropology methodology and interpretation. Archaeologists are able to distinguish between occasions when humans were handled like any other carcass and times when they were handled in more symbolic ways thanks to factors like cut mark orientation, the timing of bone breakage, and direct comparison with animal remains. Readers interested in exploring this topic further should investigate the context-specific motivations for cannibalism, like nutritional stress, warfare, funerary sites, or ritual power appropriation.
Similar archeological techniques have been used to explore behaviours of cannibalism among Indigenous Huron-Wendat populations in 1651 Canada, where human bones exhibit cutmarks, perimortem fractures, and thermal modifications (Spence & Jackson, 2014). These shared taphonomic signatures across continents reveal recurring practices under ecological stress, bridging prehistoric Europe to North American contexts. Engaging with such analytical techniques opens up new ways that archeologists and anthropologists can investigate the variability in human behaviour, from nutritional crises to mortuary rituals.
Peopling of the Americas
By 25,000 years ago, our species was the only member of Homo left on Earth. Gone were the Neanderthals, Denisovans, Homo naledi, and Homo floresiensis. The range of modern Homo sapiens kept expanding eastward into—using the name given to this area by Europeans much later—the Western Hemisphere. This section will address what we know about the peopling of the Americas, from the first entry to these continents to the rapid spread of Indigenous Americans across its varied environments.
While evidence points to an ancient land bridge called Beringia that allowed people to cross from what is now northeastern Siberia into modern-day Alaska, what people did to cross this land bridge is still being investigated. For most of the 20th century, the accepted theory was the Ice-Free Corridor model. It stated that northeast Asians (East Asians and Siberians) first expanded across Beringia inland through a passage between glaciers that opened into the western Great Plains of the United States, just east of the Rocky Mountains, around 13,000 years ago (Swisher et al. 2013). While life up north in the cold environment would have been harsh, migrating birds and an emerging forest might have provided sustenance as generations expanded through this land (Potter et al. 2018).
However, in recent decades, researchers have accumulated evidence against the Ice-Free Corridor model. Archaeologist K. R. Fladmark (1979) brought the alternate Coastal Route model into the archaeological spotlight; researcher Jon M. Erlandson has been at the forefront of compiling support for this theory (Erlandson et al. 2015). The new focus is the southern edge of the land bridge instead of its center: About 16,000 years ago, members of our species expanded along the coastline from northeast Asia, east through Beringia, and south down the Pacific Coast of North America while the inland was still sealed off by ice. The coast would have been free of ice at least part of the year, and many resources would have been found there, such as fish (e.g., salmon), mammals (e.g., whales, seals, and otters), and plants (e.g., seaweed).
South through the Americas
When the first modern Homo sapiens reached the Western Hemisphere, the spread through the Americas was rapid. Multiple migration waves crossed from North to South America (Posth et al. 2018). Our species took advantage of the lack of hominin competition and the bountiful resources both along the coasts and inland. The Americas had their own wide array of megafauna, which included woolly mammoths (Figure 13.18), mastodons, camels, horses, ground sloths, giant tortoises, and—a favorite of researchers—a two-meter-tall beaver. The reason we cannot see these amazing animals today may be that resources gained from these fauna were crucial to the survival for people over 12,000 years ago (Araujo et al. 2017). Several sites are notable for what they add to our understanding of the distant past in the Americas, including interactions with megafauna and other elements of the environment.
A 2019 discovery may allow researchers to improve theories about the peopling of the Americas. In White Sands National Park, New Mexico, 60 human footprints have been astonishingly dated to around 22,000 years ago (Bennett et al. 2021). This date and location do not match either the Ice-Free Corridor or Coastal Route models. Researchers are now working to verify the find and adjust previous models to account for the new evidence. This groundbreaking find is sparking new theories; it is another example of the fast pace of research performed on our past.
Monte Verde is a landmark site that shows that the human population had expanded down the whole vertical stretch of the Americas to Chile by 14,600 years ago. The site has been excavated by archaeologist Tom D. Dillehay and his team (2015). The remains of nine distinct edible species of seaweed at the site shows familiarity with coastal resources and relates to the Coastal Route model by showing a connection between the inland people and the sea.
Named after the town in New Mexico, the Clovis stone-tool style is the first example of a widespread culture across much of North America, between 13,400 and 12,700 years ago (Miller, Holliday, and Bright 2013). Clovis points were fluted with two small projections, one on each end of the base, facing away from the head (Figure 13.19). The stone points found at this site match those found as far as the Canadian border and northern Mexico, and from the west coast to the east coast of the United States. Fourteen Clovis sites also contained the remains of mammoths or mastodons, suggesting that hunting megafauna with these points was an important part of life for the Clovis people. After the spread of the Clovis style, it diversified into several regional styles, keeping some of the Clovis form but also developing their own unique touches.
The Big Picture: The Assimilation Hypothesis
How do researchers make sense of all of these modern Homo sapiens discoveries that cover over 300,000 years of time and stretch across every continent except Antarctica? How was modern Homo sapiens related to archaic Homo sapiens?
The Assimilation hypothesis proposes that modern Homo sapiens evolved in Africa first and expanded out but also interbred with the archaic Homo sapiens they encountered outside Africa (Figure 13.20). This hypothesis is powerful since it explains why Africa has the oldest modern human fossils, why early modern humans found in Europe and Asia bear a resemblance to the regional archaics, and why traces of archaic DNA can be found in our genomes today (Dannemann and Racimo 2018; Reich et al. 2010; Reich et al. 2011; Slatkin and Racimo 2016; Smith et al. 2017; Wall and Yoshihara Caldeira Brandt 2016).
While researchers have produced a model that satisfies the data, there are still a lot of questions for paleoanthropologists to answer regarding our origins. What were the patterns of migration in each part of the world? Why did the archaic humans go extinct? In what ways did archaic and modern humans interact? The definitive explanation of how our species started and what our ancestors did is still out there to be found. You are now in a great place to welcome the next discovery about our distant past—maybe you’ll even contribute to our understanding as well.
The Chain Reaction of Agriculture
While it may be hard to imagine today, for most of our species’ existence we were nomadic: moving through the landscape without a singular home. Instead of a refrigerator or pantry stocked with food, we procured nutrition and other resources as needed based on what was available in the environment. This section gives an overview of how the foraging lifestyle enabled the expansion of our species and how the invention of a new way of life caused a chain reaction of cultural change.
The Foraging Tradition
There are a variety of possible subsistence strategies, or methods of finding sustenance and resources. To understand our species is to understand the subsistence strategy of foraging, or the search for resources in the environment. While most (but not all) humans today live in cultures that practice agriculture (whereby we greatly shape the environment to mass produce what we need), we have spent far more time as nomadic foragers than as settled agriculturalists. As such, it has been suggested that our traits have evolved to be primarily geared toward foraging. For instance, our efficient bipedalism allows persistence-hunting across long distances as well as movement from resource to resource.
How does human foraging, also known as hunting and gathering, work? Anthropologists have used all four fields to answer this question (see Ember n.d.). Typically, people formed bands, or kin-based groups of around 50 people or less (rarely over 100). A band’s organization would be egalitarian, with a flexible hierarchy based on an individual’s age, level of experience, and relationship with others. Everyone would have a general knowledge of the skills assigned to their gender roles, rather than specializing in different occupations. A band would be able to move from place to place in the environment, using knowledge of the area to forage (Figure 13.21). In varied environments—from savannas to tropical forests, deserts, coasts, and the Arctic circle—people found sustenance needed for survival.
Humans made extensive use of the foraging subsistence strategy, but this lifestyle did have limitations. The ease of foraging depended on the richness of the environment. Due to the lack of storage, resources had to be dependably found when needed. While a bountiful environment would require just a few hours of foraging a day and could lead to a focus on one location, the level and duration of labor increased greatly in poor or unreliable environments. Labor was also needed to process the acquired resources, which contributed to the foragers’ daily schedule (Crittenden and Schnorr 2017).
The adaptations to foraging found in modern Homo sapiens may explain why our species became so successful both within Africa and in the rapid expansion around the world. Overcoming the limitations, each generation at the edge of our species’s range would have found it beneficial to expand a little further, keeping contact with other bands but moving into unexplored territory where resources were more plentiful. The cumulative effect would have been the spread of modern Homo sapiens across continents and hemispheres.
Why Agriculture?
After hundreds of thousands of years of foraging, some groups of people around 12,000 years ago started to practice agriculture. This transition, called the Neolithic Revolution, occurred at the start of the Holocene epoch. While the reasons for this global change are still being investigated, two likely co-occurring causes are a growing human population and natural global climate change.
Overcrowding could have affected the success of foraging in the environment, leading to the development of a more productive subsistence strategy (Cohen 1977). Foraging works best with low population densities since each band needs a lot of space to support itself. If too many people occupy the same environment, they deplete the area faster. The high population could exceed the carrying capacity, or number of people a location can reliably support. Reaching carrying capacity on a global level due to growing population and limited areas of expansion would have been an increasingly pressing issue after the expansion through the major continents by 14,600 years ago.
A changing global climate immediately preceded the transition to agriculture, so researchers have also explored a connection between the two events. Since the Last Glacial Maximum of 23,000 years ago, the Earth slowly warmed. Then, from 13,000 to 11,700 years ago, the temperature in most of the Northern Hemisphere dropped suddenly in a phenomenon called the Younger Dryas. Glaciers returned in Europe, Asia, and North America. In Mesopotamia, which includes the Levant, the climate changed from warm and humid to cool and dry. The change would have occurred over decades, disrupting the usual nomadic patterns and subsistence of foragers around the world. The disruption to foragers due to the temperature shift could have been a factor in spurring a transition to agriculture. Researchers Gregory K. Dow and colleagues (2009) believe that foraging bands would have clustered in the new resource-rich places where people started to direct their labor to farming the limited area. After the Younger Dryas ended, people expanded out of the clusters with their agricultural knowledge (Figure 13.22).
The double threat of the limitation of human continental expansion and the sudden global climate change may have placed bands in peril as more populations outpaced their environment’s carrying capacity. Not only had a growing population led to increased competition with other bands, but environments worldwide had shifted to create more uncertainty. As such, it has been proposed that as people in different areas around the world faced this unpredictable situation, they became the independent inventors of agriculture.
Agriculture around the World
Due to global changes to the human experience starting from 12,000 years ago, it has been suggested that cultures with no knowledge of each other turned toward intensely farming their local resources (see Figure 13.22). It is proposed that the first farmers engaged in artificial selection of their domesticates to enhance useful traits over generations. The switch to agriculture took time and effort with no guarantee of success and constant challenges (e.g. fires, droughts, diseases, and pests). The regions with the most widespread impact in the face of these obstacles became the primary centers of agriculture (Figure 13.23; Fuller 2010):
- Mesopotamia: The Fertile Crescent from the Tigris and Euphrates rivers through the Levant was where bands started to domesticate plants and animals around 12,000 years ago. The connection between the development of agriculture and the Younger Dryas was especially strong here. Farmed crops included wheat, barley, peas, and lentils. This was also where cattle, pigs, sheep, and goats were domesticated.
- South and East Asia: Multiple regions across this land had varieties of rice, millet, and soybeans by 10,000 years ago. Pigs were farmed with no connection to Mesopotamia. Chickens were also originally from this region, bred for fighting first and food second.
- New Guinea: Agriculture started here 10,000 years ago. Bananas, sugarcane, and taro were native to this island. Sweet potatoes were brought back from voyages to South America around the year C.E. 1000. No known animal farming occurred here.
- Mesoamerica: Agriculture from Central Mexico to northern South America also occurred from 10,000 years ago; it was also only plant based. Maize was a crop bred from teosinte grass, which has become one of the global staples. Beans, squash, and avocados were also grown in this region.
- The Andes: Starting around 8,000 years ago, local domesticated plants started with squash but later included potatoes, tomatoes, beans, and quinoa. Maize was brought down from Mesoamerica. The main farm animals were llamas, alpacas, and guinea pigs.
- Sub-Saharan Africa: This region went through a change 5,000 years ago called the Bantu expansion. The Bantu agriculturalists were established in West Central Africa and then expanded south and east. Native varieties of rice, yams, millet, and sorghum were grown across this area. Cattle were also domesticated here.
- Eastern North America: This region was the last major independent agriculture center, from 4,000 years ago. Squash and sunflower are the produce from this region that are most known today, though sumpweed and pitseed goosefoot were also farmed. Hunting was still the main source of animal products.
By 5,000 years ago, our species was well within the Neolithic Revolution. Agriculturalists spread to neighboring parts of the world with their domesticates, further expanding the use of this subsistence strategy. From this point, the human species changed from being primarily foragers to primarily agriculturalists with skilled control of their environments. The planet changed from mostly unaffected by human presence to being greatly transformed by humans. The revolution took millennia, but it was a true revolution as our species’ lifestyle was dramatically reshaped.
Cultural Effects of Agriculture
The worldwide adoption of agriculture altered the course of human culture and history forever. The core change in human culture due to agriculture is the move toward not moving: rather than live a nomadic lifestyle, farmers had to remain in one area to tend to their crops and livestock. The term for living bound to a certain location is sedentarism. This led to new aspects of life that were uncommon among foragers: the construction of permanent shelters and agricultural infrastructure, such as fields and irrigation, plus the development of storage technology, such as pottery, to preserve extra resources in case of future instability.
The high productivity of successful agriculture sparked further changes (Smith 2009). It is argued that since successful agriculture produced a much greater amount of food and other resources per unit of land compared to foraging, the population growth rate skyrocketed. The surplus of a bountiful harvest also provided insurance for harder times, reducing the risk of famine. Changes happened to society as well. With a few farming households producing enough food to feed many others, other people could focus on other tasks. So began specialization into different occupations such as craftspeople, traders, religious figures, and artists, spurring innovation in these areas as people could now devote time and effort toward specific skills. These interdependent people would settle an area together for convenience. The growth of these settlements led to urbanization, the founding of cities that became the foci of human interaction (Figure 13.24).
The formation of cities led to new issues that sparked the growth of further specializations, called institutions. These are cultural constructs that exist beyond the individual and have wide control over a population. Leadership of these cities became hierarchical with different levels of rank and control. The stratification of society increased social inequality between those with more or less power over others. Under leadership, people built impressive monumental architecture, such as pyramids and palaces, that embodied the wealth and power of these early cities. Alliances could unite cities, forming the earliest states. In several regions of the world, state organization expanded into empires, wide-ranging political entities that covered a variety of cultures.
Urbanization brought new challenges as well. The concentration of sedentary peoples was ideal for infectious diseases to thrive since they could jump from person to person and even from livestock to person (Armelagos, Brown, and Turner 2005). While successful agriculture provided a large surplus of food to thwart famine, the food produced offered less diverse food sources than foragers’ diets (Cohen and Armelagos 1984; Cohen and Crane-Kramer 2007). This shift in nutrition caused other diseases to flourish among those who adopted farming, such as dental cavities and malocclusion (the misalignment of teeth caused by soft, agricultural diets). The need to extract “wisdom teeth” or third molars seen in agricultural cultures today stems from this misalignment between the environment our ancestors adapted to and our lifestyles today.
As the new disease trends show, the adoption of agriculture and the ensuing cultural changes were not entirely positive. It is also important to note that this is not an absolutely linear progression of human culture from simple to complex. In many cases, empires have collapsed and, in some cases, cities dispersed to low-density bands that rejected institutions. However, a global trend has emerged since the adoption of agriculture, wherein population and social inequality have increased, leading to the massive and influential nation-states of today.
The rise of states in Europe has a direct impact on many of this book’s topics. Science started as a European cultural practice by the upper class that became a standardized way to study the world. Education became an institution to provide a standardized path toward producing and gaining knowledge. The scientific study of human diversity, embroiled in the race concept that still haunts us today, was connected to the European slave trade and colonialism.
Also starting in Europe, the Industrial Revolution of the 19th century turned cities into centers of mass manufacturing and spurred the rapid development of inventions (Figure 13.25). In the technologically interconnected world of today, human society has reached a new level of complexity with globalization. In this system, goods are mass-produced and consumed in different parts of the world, weakening the reliance on local farms and factories. The imbalanced relationship between consumers and producers of goods further increases economic inequality.
As states based on agriculture and industry keep exerting influence on humanity today, there are people, like the Hadzabe of Tanzania, who continue to live a lifestyle centered on foraging. Due to the overwhelming force that agricultural societies exert, foragers today have been marginalized to live in the least habitable parts of the world—the areas that are not conducive to farming, such as tropical rainforests, deserts, and the Arctic (Headland et al. 1989). Foragers can no longer live in the abundant environments that humans would have enjoyed before the Neolithic Revolution. Interactions with agriculturalists are typically imbalanced, with trade and other exchanges heavily favoring the larger group. One of anthropology’s important roles today is to intelligently and humanely manage equitable interactions between people of different backgrounds and levels of influence.
Special Topic: Indigenous Land Management
Insight into the lives of past modern humans has evolved as researchers revise previous theories and establish new connections with Indigenous knowledge holders.
The outdated view of foraging held that people lived off of the land without leaving an impact on the environment. Accompanying this idea was anthropologist Marshall Sahlins’s (1968) proposal that foragers were the “original affluent society” since they were meeting basic needs and achieving satisfaction with less work hours than agriculturalists and city-dwellers. This view countered an earlier idea that foragers were always on the brink of starvation. Sahlins’s theory took hold in the public eye as an attractive counterpoint to our busy contemporary lives in which we strive to meet our endless wants.
A fruitful type of study involving researchers collaborating with Indigenous experts has found that foragers did not just live off the land with minimal effort nor were they barely surviving in unchanging environments. Instead, they shaped the landscape to their needs using labor and strategies that were more subtle than what European colonizers and subsequent researchers were used to seeing. Research from two regions shows the latest developments in understanding Indigenous land management.
In British Columbia, Canada, the bridging of scientific and Indigenous perspectives has shown that the forests of the region are not untouched wilderness but, rather, have been crafted by Indigenous peoples thousands of years ago. Forest gardens adjacent to archaeological sites show higher plant diversity than unmanaged places even after 150 years (Armstrong et al. 2021). On the coast, 3,500-year-old archaeological sites are evidence of constructed clam gardens, according to Indigenous experts (Lepofsky et al. 2015). Another project, in consultation with Elders of the T’exelc (William Lakes First Nation) in British Columbia, introduced researchers to explanations of how forests were managed before the practice was disrupted by European colonialism (Copes-Gerbitz et al. 2021). Careful management of controlled fires reduced the density of the forest to favor plants such as raspberries and allow easier movement through the landscape.
Similarly, the study of landscapes in Australia, in consultation with Aboriginal Australians today, shows that areas previously considered wilderness by scientists were actually the result of controlling fauna and fires. The presence of grasslands with adjacent forests were purposely constructed to attract kangaroos for hunting (Gammage 2008). People also managed other animal and insect life, from emus to caterpillars. In Tasmania, a shift from productive grassland to wildfire-prone rainforest occurred after Aboriginal Australian land management was replaced by British colonial rule (Fletcher, Hall, and Alexander 2021). The site of Budj Bim of the Gunditjmara people has archaeological features of aquaculture, or the farming of fish, that date back 6,600 years (McNiven et al. 2012; McNiven et al. 2015). These examples show that Indigenous knowledge of how to manipulate the environment may be invaluable at the state level, such as by creating an Aboriginal ranger program to guide modern land management.
The Future of Humanity
A common question stemming from understanding human evolution is: What will the genetic and biological traits of our species be hundreds of thousands of years in the future? When faced with this question, people tend to think of directional selection. Maybe our braincases will be even larger, resembling the large-headed and small-bodied aliens of science fiction (Figure 13.26). Or, our hands could be specialized for interacting with our touch-based technology with less risk of repetitive injury. These ideas do not stand up to scrutiny. Since natural selection is based on adaptations that increase reproductive success, any directional change must be due to a higher rate of producing successful offspring compared to other alleles. Larger brains and more agile fingers would be convenient to possess, but they do not translate into an increase in the underlying allele frequencies.
Scientists are hesitant to professionally speculate on the unknowable, and we will never know what is in store for our species one thousand or one million years from now, but there are two trends in human evolution that may carry on into the future: increased genetic variation and a reduction in regional differences.
Rather than a directional change, genetic variation in our species could expand. Our technology can protect us from extreme environments and pathogens, even if our biological traits are not tuned to handle these stressors. The rapid pace of technological advancement means that biological adaptations will become less and less relevant to reproductive success, so nonbeneficial genetic traits will be more likely to remain in the gene pool. Biological anthropologist Jay T. Stock (2008) views environmental stress as needing to defeat two layers of protection before affecting our genetics. The first layer is our cultural adaptations. Our technology and knowledge can reduce pressure on one’s genotype to be “just right” to pass to the next generation. The second defense is our flexible physiology, such as our acclimatory responses. Only stressors not handled by these powerful responses would then cause natural selection on our alleles. These shields are already substantial, and cultural adaptations will only keep increasing in strength.
The increasing ability to travel far from one’s home region means that there will be a mixing of genetic variation on a global level in the future of our species. In recent centuries, gene flow of people around the world has increased, creating admixture in populations that had been separated for tens of thousands of years. For skin color, this means that populations all around the world could exhibit the whole range of skin colors, rather than the current pattern of decreasing melanin pigment farther from the equator. The same trend of intermixing would apply to all other traits, such as blood types. While our genetics will become more varied, the variation will be more intermixed instead of regionally isolated.
Our distant descendants will not likely be dextrous ultraintellectuals; more likely, they will be a highly variable and mobile species supported by novel cultural adaptations that make up for any inherited biological limitations. Technology may even enable the editing of DNA directly, changing these trends. With the uncertainty of our future, these are just the best-educated guesses for now. Our future is open and will be shaped little by little by the environment, our actions, and the actions of our descendants.
Summary
Modern Homo sapiens is the species that took the hominin lifestyle the furthest to become the only living member of that lineage. The largest factor that allowed us to persist while other hominins went extinct was likely our advanced ability to culturally adapt to a wide variety of environments. Our species, with its skeletal and behavioral traits, was well-suited to be generalist-specialists who successfully foraged across most of the world’s environments. The biological basis of this adaptation was our reorganized brain that facilitated innovation in cultural adaptations and intelligence for leveraging our social ties and finding ways to acquire resources from the environment. As the brain’s ability increased, it shaped the skull by reducing the evolutionary pressure to have large teeth and robust cranial bones to produce the modern Homo sapiens face.
Our ability to be generalist-specialists is seen in the geographical range that modern Homo sapiens covered in 300,000 years. In Africa, our species formed from multiregional gene flow that loosely connected archaic humans across the continent. People then expanded out to the rest of the continental Eurasia and even further to the Americas.
For most of our species’s existence, foraging was the general subsistence strategy within which people specialized to culturally adapt to their local environment. With omnivorousness and mobility, people found ways to extract and process resources, shaping the environment in return. When resource uncertainty hit the species, people around the world focused on agriculture to have a firmer control of sustenance. The new strategy shifted human history toward exponential growth and innovation, leading to our high dependence on cultural adaptations today.
While a cohesive image of our species has formed in recent years, there is still much to learn about our past. The work of many driven researchers shows that there are amazing new discoveries made all the time that refine our knowledge of human evolution. Technological innovations such as DNA analysis enable scientists to approach lingering questions from new angles. The answers we get allow us to ask even more insightful questions that will lead us to the next revelation. Like the pink limestone strata at Jebel Irhoud, previous effort has taken us so far and you are now ready to see what the next layer of discovery holds.
Hominin Species Summary
|
Hominin |
Modern Homo sapiens |
|
Dates |
315,000 years ago to present |
|
Region(s) |
Starting in Africa, then expanding around the world |
|
Famous discoveries |
Cro-Magnon individuals, discovered 1868 in Dordogne, France. Otzi the Ice Man, discovered 1991 in the Alps between Austria and Italy. Kennewick man, discovered 1996 in Washington state. |
|
Brain size |
1400 cc average |
|
Dentition |
Extremely small with short cusps. |
|
Cranial features |
An extremely globular brain case and gracile features throughout the cranium. The mandibular symphysis forms a chin at the anterior-most point. |
|
Postcranial features |
Gracile skeleton adapted for efficient bipedal locomotion at the expense of the muscular strength of most other large primates. |
|
Culture |
Extremely extensive and varied culture with many spoken and written languages. Art is ubiquitous. Technology is broad in complexity and impact on the environment. |
|
Other |
The only living hominin. Chimpanzees and bonobos are the closest living relatives. |
Review Questions
- What are the skeletal and behavioral traits that define modern Homo sapiens? What are the evolutionary explanations for its presence?
- What are some creative ways that researchers have learned about the past by studying fossils and artifacts?
- How do the discoveries mentioned in “First Africa, Then the World” fit the Assimilation model?
- What is foraging? What adaptations do we have for this subsistence strategy? Could you train to be a skilled forager?
- What are aspects of your life that come from dependence on agriculture and its cultural effects? Where did the ingredients of your favorite foods originate from?
Key Terms
African multiregionalism: The idea that modern Homo sapiens evolved as a complex web of small regional populations with sporadic gene flow among them.
Agriculture: The mass production of resources through farming and domestication.
Aquaculture: The farming of fish using techniques such as trapping, channels, and artificial ponds.
Assimilation hypothesis: Current theory of modern human origins stating that the species evolved first in Africa and interbred with archaic humans of Europe and Asia.
Atlatl: A handheld spear thrower that increased the force of thrown projectiles.
Band: A small group of people living together as foragers.
Beringia: Ancient landmass that connected Siberia and Alaska. The ancestors of Indigenous Americans would have crossed this area to reach the Americas.
Carrying capacity: The amount of organisms that an environment can reliably support.
Coastal Route model: Theory that the first Paleoindians crossed to the Americas by following the southern coast of Beringia.
Early Modern Homo sapiens, Early Anatomically Modern Human: Terms used to refer to transitional fossils between archaic and modern Homo sapiens that have a mosaic of traits. Humans like ourselves, who mostly lack archaic traits, are referred to as Late Modern Homo sapiens and simply Anatomically Modern Humans.
Egalitarian: Human organization without strict ranks. Foraging societies tend to be more egalitarian than those based on other subsistence strategies.
Foraging: Lifestyle consisting of frequent movement through the landscape and acquiring resources with minimal storage capacity.
Generalist-specialist niche: The ability to survive in a variety of environments by developing local expertise. Evolution toward this niche may have been what allowed modern Homo sapiens to expand past the geographical range of other human species.
Globalization: A recent increase in the interconnectedness and interdependence of people that is facilitated with long-distance networks.
Globular: Having a rounded appearance. Increased globularity of the braincase is a trait of modern Homo sapiens.
Gracile: Having a smooth and slender quality; the opposite of robust.
Holocene: The epoch of the Cenozoic Era starting around 12,000 years ago and lasting arguably through the present.
Ice-Free Corridor model: Theory that the first Native Americans crossed to the Americas through a passage between glaciers.
Institutions: Long-lasting and influential cultural constructs. Examples include government, organized religion, academia, and the economy.
Last Glacial Maximum: The time 23,000 years ago when the most recent ice age was the most intense.
Later Stone Age: Time period following the Middle Stone Age with a diversification in tool types, starting around 50,000 years ago.
Levant: The eastern coast of the Mediterranean. The site of early modern human expansion from Africa and later one of the centers of agriculture.
Megafauna: Large ancient animals that may have been hunted to extinction by people around the world.
Mental eminence: The chin on the mandible of modern H. sapiens. One of the defining traits of our species.
Microlith: Small stone tool found in the Later Stone Age; also called a bladelet.
Middle Stone Age: Time period known for Mousterian lithics that connects African archaic to modern Homo sapiens.
Monumental architecture: Large and labor-intensive constructions that signify the power of the elite in a sedentary society. A common type is the pyramid, a raised crafted structure topped with a point or platform.
Mosaic: Composed from a mix or composite of traits.
Neolithic Revolution: Time of rapid change to human cultures due to the invention of agriculture, starting around 12,000 years ago.
Ochre: Iron-based mineral pigment that can be a variety of yellows, reds, and browns. Used by modern human cultures worldwide since at least 80,000 years ago.
Sahul: Ancient landmass connecting New Guinea and Australia.
Sedentarism: Lifestyle based on having a stable home area; the opposite of nomadism.
Southern Dispersal model: Theory that modern H. sapiens expanded from East Africa by crossing the Red Sea and following the coast east across Asia.
Subsistence strategy: The method an organism uses to find nourishment and other resources.
Sunda: Ancient Asian landmass that incorporated modern Southeast Asia.
Supraorbital torus: The bony brow ridge across the top of the eye orbits on many hominin crania.
Upper Paleolithic: Time period considered synonymous with the Later Stone Age.
Urbanization: The increase of population density as people settled together in cities.
Wallacea: Archipelago southeast of Sunda with different biodiversity than Asia.
Younger Dryas: The rapid change in global climate—notably a cooling of the Northern Hemisphere—13,000 years ago.
For Further Exploration
Websites
First-person virtual tour of Lascaux cave with annotated cave art: Ministère de la Culture and Musée d’Archéologie Nationale. “Visit the cave” Lascaux website.
Online anthropology magazine articles related to paleoanthropology and human evolution: SAPIENS. “Evolution.” SAPIENS website.
Various presentations of information about hominin evolution: Smithsonian Institution. “What does it mean to be human?” Smithsonian National Museum of Natural History website.
Magazine-style articles on archaeology and paleoanthropology: ThoughtCo. “Archaeology.” ThoughtCo. Website.
Database of comparisons across hominins and primates: University of California, San Diego. “MOCA Domains.” Center for Academic Research & Training in Anthropogeny website.
Books
Engaging book that covers human-made changes to the environment with industrialization and globalization: Kolbert, Elizabeth. 2014. The Sixth Extinction: An Unnatural History. New York: Bloomsbury.
Overview of what human life was like among the environmental shifts of the Ice Age: Woodward, Jamie. 2014. The Ice Age: A Very Short Introduction. Oxford: OUP Press.
Articles
Recent review paper about the current state of paleoanthropology research: Stringer, C. 2016. “The Origin and Evolution of Homo sapiens.” Philosophical Transactions of the Royal Society B 371 (1698).
Overview of the history of American paleoanthropology and the many debates that have occurred over the years: Trinkaus, E. 2018. “One Hundred Years of Paleoanthropology: An American Perspective.” American Journal of Physical Anthropology 165 (4): 638–651.
Amazing magazine article that synthesizes hominin evolution and why it is important to study this subject: Wheelwright, Jeff. 2015. “Days of Dysevolution.” Discover 36 (4): 33–39.
Fascinating research on Ötzi, a mummy from 5,000 years ago: Wierer, Ursula, Simona Arrighi, Stefano Bertola, Günther Kaufmann, Benno Baumgarten, Annaluisa Pedrotti, Patrizia Pernter, and Jacques Pelegrin. 2018. “The Iceman’s Lithic Toolkit: Raw Material, Technology, Typology and Use.” PLOS One 13 (6): e0198292. https://doi.org/10.1371/journal.pone.0198292.
Documentaries
PBS NOVA series covering the expansion of modern Homo sapiens and interbreeding with archaic humans: Brown, Nicholas, dir. 2015. First Peoples. Edmonton: Wall to Wall Television. Amazon Prime Video.
PBS NOVA special featuring the footprints found in White Sands National Park: Falk, Bella, dir. 2016. Ice Age Footprints. Boston: Windfall Films. https://www.pbs.org/wgbh/nova/video/ice-age-footprints/.
PBS NOVA special about how modern humans evolved adaptations to different environments. Shows how present-day people live around the world: Thompson, Niobe, dir. 2016. Great Human Odyssey. Edmonton: Clearwater Documentary. https://www.pbs.org/wgbh/nova/evolution/great-human-odyssey.html.
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Acknowledgments
I could not have undertaken this project without the help of many who got me to where I am today. I extend sincere thank yous to the many colleagues and former students who have inspired me to keep learning and talking about anthropology. Thank you also to all who are involved in this textbook project. The anonymous reviewers truly sparked improvements to the chapter. Lastly, the staff of Starbucks #5772 also contributed immensely to this text.
Keith Chan, Ph.D., Grossmont-Cuyamaca Community College District and MiraCosta College
This chapter is a revision from "Chapter 12: Modern Homo sapiens” by Keith Chan. In Explorations: An Open Invitation to Biological Anthropology, first edition, edited by Beth Shook, Katie Nelson, Kelsie Aguilera, and Lara Braff, which is licensed under CC BY-NC 4.0.
Learning Objectives
- Identify the skeletal and behavioral traits that represent modern Homo sapiens.
- Critically evaluate different types of evidence for the origin of our species in Africa and our expansion around the world.
- Understand how the human lifestyle changed when people transitioned from foraging to agriculture.
- Hypothesize how human evolutionary trends may continue into the future.
The walls of a pink limestone cave in the hillside of Jebel Irhoud jutted out of the otherwise barren landscape of the Moroccan desert (Figure 13.1). Miners had excavated the cave in the 1960s, revealing some fossils. In 2007, a re-excavation of the site became a momentous occasion for science. A fossil cranium unearthed by a team of researchers was barely visible to the untrained eye. Just the fossil’s robust brows were peering out of the rock. This research team from the Max Planck Institute for Evolutionary Anthropology was the latest to explore the ancient human presence in this part of North Africa after a find by miners in 1960. Excavating near the first discovery, the researchers wanted to learn more about how Homo sapiens lived far from East Africa, where we thought our species originated.
The scientists were surprised when they analyzed the cranium, named Irhoud 10, and other fossils. Statistical comparisons with other human crania concluded that the Irhoud face shapes were typical of recent modern humans while the braincases matched ancient modern humans. Based on the findings of other scientists, the team expected these modern Homo sapiens fossils to be around 200,000 years old. Instead, dating revealed that the cranium had been buried for around 315,000 years.
Together, the modern-looking facial dimensions and the older date reshaped the interpretation of our species: modern Homo sapiens. Some key evolutionary changes from the archaic Homo sapiens (described in Chapter 11) to our species today happened 100,000 years earlier than we had thought and across the vast African continent rather than concentrated in its eastern region.
This revelation in the study of modern Homo sapiens is just one of the latest in this continually advancing area of biological anthropology. Researchers today are still discovering amazing fossils and ingenious ways to collect data and test hypotheses about our past. Through the collective work of many scientists, we are building an overall theory of modern human origins.
Defining Modernity
What defines modern Homo sapiens when compared to archaic Homo sapiens? Modern humans, like you and me, have a set of derived traits that are not seen in archaic humans or any other hominin. As with other transitions in hominin evolution, such as increasing brain size and bipedal ability, modern traits do not appear fully formed or all at once. In other words, the first modern Homo sapiens was not just born one day from archaic parents. The traits common to modern Homo sapiens appeared in a mosaic manner: gradually and out of sync with one another. There are two areas to consider when tracking the complex evolution of modern human traits. One is the physical change in the skeleton. The other is behavior inferred from the size and shape of the cranium and material culture evidence.
Skeletal Traits
The skeleton of modern Homo sapiens is less robust than that of archaic Homo sapiens. In other words, the modern skeleton is gracile, meaning that the structures are thinner and smoother. Differences related to gracility in the cranium are seen in the braincase, the face, and the mandible. There are also broad differences in the rest of the skeleton.
Cranial Traits
Several elements of the braincase differ between modern and archaic Homo sapiens. Overall, the shape is much rounder, or more globular, on a modern skull (Lieberman, McBratney, and Krovitz 2002; Neubauer, Hublin, and Gunz 2018; Pearson 2008; Figure 13.2). You can feel the globularity of your own modern human skull. Feel the height of your forehead with the palm of your hand. Viewed from the side, the tall vertical forehead of a modern Homo sapiens stands out when compared to the sloping archaic version. This is because the frontal lobe of the modern human brain is larger than the one in archaic humans, and the skull has to accommodate the expansion. The vertical forehead reduces a trait that is common to all other hominins: the brow ridge or supraorbital torus. The parietal lobes of the brain and the matching parietal bones on either side of the skull both bulge outward more in modern humans. At the back of the skull, the archaic occipital bun is no longer present. Instead, the occipital region of the modern human cranium has a derived tall and smooth curve, again reflecting the globular brain inside.
The trend of shrinking face size across hominins reaches its extreme with our species as well. The facial bones of a modern Homo sapiens are extremely gracile compared to all other hominins (Lieberman, McBratney, and Krovitz 2002). Continuing a trend in hominin evolution, technological innovations kept reducing the importance of teeth in reproductive success (Lucas 2007). As natural selection favored smaller and smaller teeth, the surrounding bone holding these teeth also shrank.
Related to smaller teeth, the mandible is also gracile in modern humans when compared to archaic humans and other hominins. Interestingly, our mandibles have pulled back so far from the prognathism of earlier hominins that we gained an extra structure at the most anterior point, called the mental eminence. You know this structure as the chin. At the skeletal level, it resembles an upside-down “T” at the centerline of the mandible (Pearson 2008). Looking back at archaic humans, you will see that they all lack a chin. Instead, their mandibles curve straight back without a forward point. What is the chin for and how did it develop? Flora Gröning and colleagues (2011) found evidence of the chin’s importance by simulating physical forces on computer models of different mandible shapes. Their results showed that the chin acts as structural support to withstand strain on the otherwise gracile mandible.
Postcranial Gracility
The rest of the modern human skeleton is also more gracile than its archaic counterpart. The differences are clear when comparing a modern Homo sapiens with a cold-adapted Neanderthal (Sawyer and Maley 2005), but the trends are still present when comparing modern and archaic humans within Africa (Pearson 2000). Overall, a modern Homo sapiens postcranial skeleton has thinner cortical bone, smoother features, and more slender shapes when compared to archaic Homo sapiens (Figure 13.3). Comparing whole skeletons, modern humans have longer limb proportions relative to the length and width of the torso, giving us lankier outlines.
Why is our skeleton so gracile compared to those of other hominins? Natural selection can drive the gracilization of skeletons in several ways (Lieberman 2015). A slender frame is believed to be adapted for the efficient long-distance running ability that started with Homo erectus. Furthermore, it is argued that slenderness is a genetic adaptation for cooling an active body in hotter climates, which aligns with the ample evidence that Africa was the home continent of our species.
Behavioral Modernity
Aside from physical differences in the skeleton, researchers have also uncovered evidence of behavioral changes associated with increased cultural complexity from archaic to modern humans. How did cultural complexity develop? Two investigations into this question are archaeology and the analysis of reconstructed brains.
Archaeology tells us much about the behavioral complexity of past humans by interpreting the significance of material culture. In terms of advanced culture, items created with an artistic flair, or as decoration, speak of abstract thought processes (Figure 13.4). The demonstration of difficult artistic techniques and technological complexity hints at social learning and cooperation as well. According to paleoanthropologist John Shea (2011), one way to track the complexity of past behavior through artifacts is by measuring the variety of tools found together. The more types of tools constructed with different techniques and for different purposes, the more modern the behavior. Researchers are still working on an archaeological way to measure cultural complexity that is useful across time and place.
The interpretation of brain anatomy is another promising approach to studying the evolution of human behavior. When looking at investigations on this topic in modern Homo sapiens brains, researchers found a weak association between brain size and test-measured intelligence (Pietschnig et al. 2015). Additionally, they found no association between intelligence and biological sex. These findings mean that there are more significant factors that affect tested intelligence than just brain size. Since the sheer size of the brain is not useful for weighing intelligence within a species, paleoanthropologists are instead investigating the differences in certain brain structures. The differences in organization between modern Homo sapiens brains and archaic Homo sapiens brains may reflect different cognitive priorities that account for modern human culture. As with the archaeological approach, new discoveries will refine what we know about the human brain and apply that knowledge to studying the distant past.
Taken together, the cognitive abilities in modern humans may have translated into an adept use of tools to enhance survival. Researchers Patrick Roberts and Brian A. Stewart (2018) call this concept the generalist-specialist niche: our species is an expert at living in a wide array of environments, with populations culturally specializing in their own particular surroundings. The next section tracks how far around the world these skeletal and behavioral traits have taken us.
First Africa, Then the World
What enabled modern Homo sapiens to expand its range further in 300,000 years than Homo erectus did in 1.5 million years? The key is the set of derived biological traits from the last section. It is theorized that the gracile frame and neurological anatomy allowed modern humans to survive and even flourish in the vastly different environments they encountered. Based on multiple types of evidence, the source of all of these modern humans was Africa. Instead of originating from just one location, evidence shows that modern Homo sapiens evolution occurred in a complex gene flow network across Africa, a concept called African multiregionalism (Scerri et al. 2018).
This section traces the origin of modern Homo sapiens and the massive expansion of our species across all of the continents (except Antarctica) by 12,000 years ago. While modern Homo sapiens first shared geography with archaic humans, modern humans eventually spread into lands where no human had gone before. Figure 13.5 shows the broad routes that our species took expanding around the world. I encourage you to make your own timeline with the dates in this part to see the overall trends.
Modern Homo sapiens Biology and Culture in Africa
We start with the ample fossil evidence supporting the theory that modern humans originated in Africa during the Middle Pleistocene, having evolved from African archaic Homo sapiens. The earliest dated fossils considered to be modern actually have a mosaic of archaic and modern traits, showing the complex changes from one type to the other. Experts have various names for these transitional fossils, such as Early Modern Homo sapiens or Early Anatomically Modern Humans. However they are labeled, the presence of some modern traits means that they illustrate the origin of the modern type. Three particularly informative sites with fossils of the earliest modern Homo sapiens are Jebel Irhoud, Omo, and Herto.
Recall from the start of the chapter that the most recent finds at Jebel Irhoud are now the oldest dated fossils that exhibit some facial traits of modern Homo sapiens. Besides Irhoud 10, the cranium that was dated to 315,000 years ago (Hublin et al. 2017; Richter et al. 2017), there were other fossils found in the same deposit that we now know are from the same time period. In total there are at least five individuals, representing life stages from childhood to adulthood. These fossils form an image of high variation in skeletal traits. For example, the skull named Irhoud 1 has a primitive brow ridge, while Irhoud 2 and Irhoud 10 do not (Figure 13.6). The braincases are lower than what is seen in the modern humans of today but higher than in archaic Homo sapiens. The teeth also have a mix of archaic and modern traits that defy clear categorization into either group.
Research separated by nearly four decades uncovered fossils and artifacts from the Kibish Formation in the Lower Omo Valley in Ethiopia. These Omo Kibish hominins were represented by braincases and fragmented postcranial bones of three individuals found kilometers apart, dating back to around 233,000 years ago (Day 1969; McDougall, Brown, and Fleagle 2005; Vidal et al. 2022). One interesting finding was the variation in braincase size between the two more-complete specimens: while the individual named Omo I had a more globular dome, Omo II had an archaic-style long and low cranium.
Also in Ethiopia, a team led by Tim White (2003) excavated numerous fossils at Herto. There were fossilized crania of two adults and a child, along with fragments of more individuals. The dates ranged between 160,000 and 154,000 years ago. The skeletal traits and stone-tool assemblage were both intermediate between the archaic and modern types. Features reminiscent of modern humans included a tall braincase and thinner zygomatic (cheek) bones than those of archaic humans (Figure 13.7). Still, some archaic traits persisted in the Herto fossils, such as the supraorbital tori. Statistical analysis by other research teams concluded that at least some cranial measurements fit just within the modern human range (McCarthy and Lucas 2014), favoring categorization with our own species.
The timeline of material culture suggests a long period of relying on similar tools before a noticeable diversification of artifacts types. Researchers label the time of stable technology shared with archaic types the Middle Stone Age, while the subsequent time of diversification in material culture is called the Later Stone Age.
In the Middle Stone Age, the sites of Jebel Irhoud, Omo, and Herto all bore tools of the same flaked style as archaic assemblages, even though they were separated by almost 150,000 years. The consistency in technology may be evidence that behavioral modernity was not so developed. No clear signs of art dating back this far have been found either. Other hypotheses not related to behavioral modernity could explain these observations. The tool set may have been suitable for thriving in Africa without further innovation. Maybe works of art from that time were made with media that deteriorated or perhaps such art was removed by later humans.
Evidence of what Homo sapiens did in Africa from the end of the Middle Stone Age to the Later Stone Age is concentrated in South African cave sites that reveal the complexity of human behavior at the time. For example, Blombos Cave, located along the present shore of the Cape of Africa facing the Indian Ocean, is notable for having a wide variety of artifacts. The material culture shows that toolmaking and artistry were more complex than previously thought for the Middle Stone Age. In a layer dated to 100,000 years ago, researchers found two intact ochre-processing kits made of abalone shells and grinding stones (Henshilwood et al. 2011). Marine snail shell beads from 75,000 years ago were also excavated (Figure 13.8; d’Errico et al. 2005). Together, the evidence shows that the Middle Stone Age occupation at Blombos Cave incorporated resources from a variety of local environments into their culture, from caves (ochre), open land (animal bones and fat), and the sea (abalone and snail shells). This complexity shows a deep knowledge of the region’s resources and their use—not just for survival but also for symbolic purposes.
On the eastern coast of South Africa, Border Cave shows new African cultural developments at the start of the Later Stone Age. Paola Villa and colleagues (2012) identified several changes in technology around 43,000 years ago. Stone-tool production transitioned from a slower process to one that was faster and made many microliths, small and precise stone tools. Changes in decorations were also found across the Later Stone Age transition. Beads were made from a new resource: fragments of ostrich eggs shaped into circular forms resembling present-day breakfast cereal O’s (d’Errico et al. 2012). These beads show a higher level of altering one’s own surroundings and a move from the natural to the abstract in terms of design.
Expansion into the Middle East and Asia
While modern Homo sapiens lived across Africa, some members eventually left the continent. These pioneers could have used two connections to the Middle East or West Asia. From North Africa, they could have crossed the Sinai Peninsula and moved north to the Levant, or eastern Mediterranean. Finds in that region show an early modern human presence. Other finds support the Southern Dispersal model, with a crossing from East Africa to the southern Arabian Peninsula through the Straits of Bab-el-Mandeb. It is tempting to think of one momentous event in which people stepped off Africa and into the Middle East, never to look back. In reality, there were likely multiple waves of movement producing gene flow back and forth across these regions as the overall range pushed east. The expanding modern human population could have thrived by using resources along the southern coast of the Arabian Peninsula to South Asia, with side routes moving north along rivers. The maximum range of the species then grew across Asia.
Modern Homo sapiens in the Middle East
Geographically, the Middle East is the ideal place for the African modern Homo sapiens population to inhabit upon expanding out of their home continent. In the Eastern Mediterranean coast of the Levant, there is a wealth of skeletal and material culture linked to modern Homo sapiens. Recent discoveries from Saudi Arabia further add to our view of human life just beyond Africa.
The Caves of Mount Carmel in present-day Israel have preserved skeletal remains and artifacts of modern Homo sapiens, the first-known group living outside Africa. The skeletal presence at Misliya Cave is represented by just part of the left upper jaw of one individual, but it is notable for being dated to a very early time, between 194,000 and 177,000 years ago (Hershkovitz et al. 2018). Later, from 120,000 to 90,000 years ago, fossils of multiple individuals across life stages were found in the caves of Es-Skhul and Qafzeh (Shea and Bar-Yosef 2005). The skeletons had many modern Homo sapiens traits, such as globular crania and more gracile postcranial bones when compared to Neanderthals. Still, there were some archaic traits. For example, the adult male Skhul V also possessed what researchers Daniel Lieberman, Osbjorn Pearson, and Kenneth Mowbray (2000) called marked or clear occipital bunning. Also, compared to later modern humans, the Mount Carmel people were more robust. Skhul V had a particularly impressive brow ridge that was short in height but sharply jutted forward above the eyes (Figure 13.9). The high level of preservation is due to the intentional burial of some of these people. Besides skeletal material, there are signs of artistic or symbolic behavior. For example, the adult male Skhul V had a boar’s jaw on his chest. Similarly, Qafzeh 11, a juvenile with healed cranial trauma, had an impressive deer antler rack placed over his torso (Figure 13.10; Coqueugniot et al. 2014). Perforated seashells colored with ochre, mineral-based pigment, were also found in Qafzeh (Bar-Yosef Mayer, Vandermeersch, and Bar-Yosef 2009).
One remaining question is, what happened to the modern humans of the Levant after 90,000 years ago? Another site attributed to our species did not appear in the region until 47,000 years ago. Competition with Neanderthals may have accounted for the disappearance of modern human occupation since the Neanderthal presence in the Levant lasted longer than the dates of the early modern Homo sapiens. John Shea and Ofer Bar-Yosef (2005) hypothesized that the Mount Carmel modern humans were an initial expansion from Africa that failed. Perhaps they could not succeed due to competition with the Neanderthals who had been there longer and had both cultural and biological adaptations to that environment.
Modern Homo sapiens of China
A long history of paleoanthropology in China has found ample evidence of modern human presence. Four notable sites are the caves at Fuyan, Liujiang, Tianyuan, and Zhoukoudian. In the distant past, these caves would have been at least seasonal shelters that unintentionally preserved evidence of human presence for modern researchers to discover.
At Fuyan Cave in Southern China, paleoanthropologists found 47 adult teeth associated with cave formations dated to between 120,000 and 80,000 years ago (Liu et al. 2015). It is currently the oldest-known modern human site in China, though other researchers question the validity of the date range (Michel et al. 2016). The teeth have the small size and gracile features of modern Homo sapiens dentition.
The fossil Liujiang (or Liukiang) hominin (67,000 years ago) has derived traits that classified it as a modern Homo sapiens, though primitive archaic traits were also present. In the skull, which was found nearly complete, the Liujiang hominin had a taller forehead than archaic Homo sapiens but also had an enlarged occipital region (Figure 13.11; Brown 1999; Wu et al. 2008). Other parts of the skeleton also had a mix of modern and archaic traits: for example, the femur fragments suggested a slender length but with thick bone walls (Woo 1959).
Another Chinese site to describe here is the one that has been studied the longest. In the Zhoukoudian Cave system (Figure 13.12), where Homo erectus and archaic Homo sapiens have also been found, there were three crania of modern Homo sapiens. These crania, which date to between 34,000 and 10,000 years ago, were all more globular than those of archaic humans but still lower and longer than those of later modern humans (Brown 1999; Harvati 2009). When compared to one another, the crania showed significant differences from one another. Comparison of cranial measurements to other populations past and present found no connection with modern East Asians, again showing that human variation was very different from what we see today.
Crossing to Australia
Expansion of the first modern human Asians, still following the coast, eventually entered an area that researchers call Sunda before continuing on to modern Australia. Sunda was a landmass made up of the modern-day Malay Peninsula, Sumatra, Java, and Borneo. Lowered sea levels connected these places with land bridges, making them easier to traverse. Proceeding past Sunda meant navigating Wallacea, the archipelago that includes the Indonesian islands east of Borneo. In the distant past, there were many megafauna, large animals that migrating humans would have used for food and materials (such as utilizing animals’ hides and bones). Further southeast was another landmass called Sahul, which included New Guinea and Australia as one contiguous continent. Based on fossil evidence, this land had never seen hominins or any other primates before modern Homo sapiens arrived. Sites along this path offer clues about how our species handled the new environment to live successfully as foragers.
The skeletal remains at Lake Mungo, land traditionally owned by Mutthi Mutthi, Ngiampaa, and Paakantji peoples, are the oldest known in the continent. The now-dry lake was one of a series located along the southern coast of Australia in New South Wales, far from where the first people entered from the north (Barbetti and Allen 1972; Bowler et al. 1970). Two individuals dating to around 40,000 years ago show signs of artistic and symbolic behavior, including intentional burial. The bones of Lake Mungo 1 (LM1), an adult female, were crushed repeatedly, colored with red ochre, and cremated (Bowler et al. 1970). Lake Mungo 3 (LM3), a tall, older male with a gracile cranium but robust postcranial bones, had his fingers interlocked over his pelvic region (Brown 2000).
Kow Swamp, within traditional Yorta Yorta land also in southern Australia, contained human crania that looked distinctly different from the ones at Lake Mungo (Durband 2014; Thorne and Macumber 1972). The crania, dated between 9,000 and 20,000 years ago, had extremely robust brow ridges and thick bone walls, but these were paired with globular features on the braincase (Figure 13.13).
While no fossil humans have been found at the Madjedbebe rock shelter in the North Territory of Australia, more than 10,000 artifacts found there show both behavioral modernity and variability (Clarkson et al. 2017). They include a diverse array of stone tools and different shades of ochre for rock art, including mica-based reflective pigment (similar to glitter). These impressive artifacts are as far back as 56,000 years old, providing the date for the earliest-known presence of humans in Australia.
From the Levant to Europe
The first modern human expansion into Europe occurred after other members of our species settled in East Asia and Australia. As the evidence from the Levant suggests, modern human movement to Europe may have been hampered by the presence of Neanderthals. It is suggested that another obstacle was the colder climate, which was incompatible with the biology of modern Homo sapiens from Africa, as they were adapted to high temperatures and ultraviolet radiation. Still, by 40,000 years ago, modern Homo sapiens had a detectable presence. This time was also the start of the Later Stone Age or Upper Paleolithic, when there was an expansion in cultural complexity. There is a wealth of evidence from this region due to a Western bias in research, the proximity of these findings to Western scientific institutions, and the desire of Western scientists to explore their own past.
In Romania, the site of Peștera cu Oase (Cave of Bones) had the oldest-known remains of modern Homo sapiens in Europe, dated to around 40,000 years ago (Trinkaus et al. 2003a). Among the bones and teeth of many animals were the fragmented cranium of one person and the mandible of another (the two bones did not fit each other). Both bones have modern human traits similar to the fossils from the Middle East, but they also had Neanderthal traits. Oase 1, the mandible, had a mental eminence but also extremely large molars (Trinkaus et al. 2003b). This mandible has yielded DNA that surprisingly is equally similar to DNA from present-day Europeans and Asians (Fu et al. 2015). This means that Oase 1 was not the direct ancestor of modern Europeans. The Oase 2 cranium has the derived traits of reduced brow ridges along with archaic wide zygomatic cheekbones and an occipital bun (Figure 13.14; Rougier et al. 2007).
Dating to around 26,000 years ago, Předmostí near Přerov in the Czech Republic was a site where people buried over 30 individuals along with many artifacts. Eighteen individuals were found in one mass burial area, a few covered by the scapulae of woolly mammoths (Germonpré, Lázničková-Galetová, and Sablin 2012). The Předmostí crania were more globular than those of archaic humans but tended to be longer and lower than in later modern humans (Figure 13.15; Velemínská et al. 2008). The height of the face was in line with modern residents of Central Europe. There was also skeletal evidence of dog domestication, such as the presence of dog skulls with shorter snouts than in wild wolves (Germonpré, Lázničková-Galetová, and Sablin et al. 2012). In total, Předmostí could have been a settlement dependent on mammoths for subsistence and the artificial selection of early domesticated dogs.
The sequence of modern Homo sapiens technological change in the Later Stone Age has been thoroughly dated and labeled by researchers working in Europe. Among them, the Gravettian tradition of 33,000 years to 21,000 years ago is associated with most of the known curvy female figurines, often assumed to be “Venus” figures. Hunting technology also advanced in this time with the first known boomerang, atlatl (spear thrower), and archery. The Magdalenian tradition spread from 17,000 to 12,000 years ago. This culture further expanded on fine bone tool work, including barbed spearheads and fishhooks (Figure 13.16).
Among the many European sites dating to the Later Stone Age, the famous cave art sites deserve mention. Chauvet-Pont-d'Arc Cave in southern France dates to separate Aurignacian occupations 31,000 years ago and 26,000 years ago. Over a hundred art pieces representing 13 animal species are preserved, from commonly depicted deer and horses to rarer rhinos and owls. Another French cave with art is Lascaux, which is several thousand years younger at 17,000 years ago in the Magdalenian period. At this site, there are over 6,000 painted figures on the walls and ceiling (Figure 13.17). Scaffolding and lighting must have been used to make the paintings on the walls and ceiling deep in the cave. Overall, visiting Lascaux as a contemporary must have been an awesome experience: trekking deeper in the cave lit only by torches giving glimpses of animals all around as mysterious sounds echoed through the galleries.
Special Topic: Cannibalism and Culture - Mortuary Practices in Modern Homo sapiens
Within a 2017 publication in the Journal of Archaeological Method and Theory, Saladié and Rodríguez-Hidalgo bring light to traces of early cannibalism in western Eurasia, arguing that context-specific cannibalistic practices were present throughout the Pleistocene and increased notably from the end of the Upper Palaeolithic and onward (Saladié & Rodriguez-Hidalgo, 2017). While early hominins and Neandertals are recognized in this research, the authors highlight the presence of these mortuary practices in a cluster of Homo Sapien sites. More recent research uncovers similar findings that back these claims as well, where human bones in Herto Ethiopia, Maszycka Cave Poland, and Gough’s Cave in the United Kingdom show anthropogenic defleshing and other modifications which have been interpreted as cannibalism (Pobiner, Et al. 2023). These findings suggest that cannibalistic behaviours formed a recurring aspect of modern human behaviour in certain ecological and cultural contexts.
A significant example comes from the Neolithic levels of Fontbrégua Cave in southeastern France, where Paola Villa and colleagues compared clusters of human bones with the remains of wild and domestic animals from the same sediments. The study found that human bodies were butchered, processed, and most likely eaten in a way that parallels animal carcass treatment, including the placement and timing of cut marks, dismemberment sequences, and perimortem fractures to open marrow cavities (Villa, Et al. 1986). As the assemblage comes from a primary depositional context with pristine preservation and careful excavation, the authors suggest that cannibalism is the only satisfactory explanation for the pattern of cut marks and breakage seen on the human bones.
More recent work has furthered this hypothesis for Late Upper Palaeolithic Homo sapiens, especially in Magdalenian contexts. In a 2023 study, researchers combined archeological and genetic evidence from fifty-nine Magdalenian sites, concluding that this specific culture shows an unusually high frequency of cannibalistic cases compared to earlier and later hominin groups; so much so that they identify “primary burial and cannibalism” as the two main mortuary expressions (Marsh & Bello, 2023). Additionally, new analyses from Maszycka Cave in Poland have described cut and broken human bones in patterns consistent with human consumption, reinforcing this cannibalism hypothesis (Marginedas & Saladié, 2025). Together, these studies suggest that for some Magdalenian groups, mortuary cannibalism was a habitual way of disposing of the dead, not just a one-off crisis response. At the same time, researchers emphasize that not every modified skeleton indicates blatant consumption of the dead and that ritual or symbolic perspectives must also be considered. Previously noted in chapter eleven, Ullrich’s survey of European mortuary practices presents frequent manipulations of corpses from the Palaeolithic through the Hallstatt period. Said manipulations include cut marks, dismemberment, skull fracturing, and marrow extraction (Ullrich, 2005, p. 258), which Ullrich interprets as cannibalistic rites embedded in cult ceremonies rather than everyday subsistence. In the author’s view, some Palaeolithic groups may have believed that consuming members of their community allowed them to take on the strengths,
abilities, or even mental aspects of their dead member; the act of cannibalism may have functioned as a form of appropriating physical and mental powers rather than simply obtaining calories. With that, Neolithic assemblages show how careful taphonomic work can distinguish cuts linked to interpersonal violence from those associated with systemic butchery (Marginedas & Saladié, 2025). The findings seek to highlight that some Homo sapiens populations combined ritual, mortuary, and nutritional motives when processing human remains.
These past and contemporary findings are significant for future anthropology students as they shed light on biological anthropology methodology and interpretation. Archaeologists are able to distinguish between occasions when humans were handled like any other carcass and times when they were handled in more symbolic ways thanks to factors like cut mark orientation, the timing of bone breakage, and direct comparison with animal remains. Readers interested in exploring this topic further should investigate the context-specific motivations for cannibalism, like nutritional stress, warfare, funerary sites, or ritual power appropriation.
Similar archeological techniques have been used to explore behaviours of cannibalism among Indigenous Huron-Wendat populations in 1651 Canada, where human bones exhibit cutmarks, perimortem fractures, and thermal modifications (Spence & Jackson, 2014). These shared taphonomic signatures across continents reveal recurring practices under ecological stress, bridging prehistoric Europe to North American contexts. Engaging with such analytical techniques opens up new ways that archeologists and anthropologists can investigate the variability in human behaviour, from nutritional crises to mortuary rituals.
Peopling of the Americas
By 25,000 years ago, our species was the only member of Homo left on Earth. Gone were the Neanderthals, Denisovans, Homo naledi, and Homo floresiensis. The range of modern Homo sapiens kept expanding eastward into—using the name given to this area by Europeans much later—the Western Hemisphere. This section will address what we know about the peopling of the Americas, from the first entry to these continents to the rapid spread of Indigenous Americans across its varied environments.
While evidence points to an ancient land bridge called Beringia that allowed people to cross from what is now northeastern Siberia into modern-day Alaska, what people did to cross this land bridge is still being investigated. For most of the 20th century, the accepted theory was the Ice-Free Corridor model. It stated that northeast Asians (East Asians and Siberians) first expanded across Beringia inland through a passage between glaciers that opened into the western Great Plains of the United States, just east of the Rocky Mountains, around 13,000 years ago (Swisher et al. 2013). While life up north in the cold environment would have been harsh, migrating birds and an emerging forest might have provided sustenance as generations expanded through this land (Potter et al. 2018).
However, in recent decades, researchers have accumulated evidence against the Ice-Free Corridor model. Archaeologist K. R. Fladmark (1979) brought the alternate Coastal Route model into the archaeological spotlight; researcher Jon M. Erlandson has been at the forefront of compiling support for this theory (Erlandson et al. 2015). The new focus is the southern edge of the land bridge instead of its center: About 16,000 years ago, members of our species expanded along the coastline from northeast Asia, east through Beringia, and south down the Pacific Coast of North America while the inland was still sealed off by ice. The coast would have been free of ice at least part of the year, and many resources would have been found there, such as fish (e.g., salmon), mammals (e.g., whales, seals, and otters), and plants (e.g., seaweed).
South through the Americas
When the first modern Homo sapiens reached the Western Hemisphere, the spread through the Americas was rapid. Multiple migration waves crossed from North to South America (Posth et al. 2018). Our species took advantage of the lack of hominin competition and the bountiful resources both along the coasts and inland. The Americas had their own wide array of megafauna, which included woolly mammoths (Figure 13.18), mastodons, camels, horses, ground sloths, giant tortoises, and—a favorite of researchers—a two-meter-tall beaver. The reason we cannot see these amazing animals today may be that resources gained from these fauna were crucial to the survival for people over 12,000 years ago (Araujo et al. 2017). Several sites are notable for what they add to our understanding of the distant past in the Americas, including interactions with megafauna and other elements of the environment.
A 2019 discovery may allow researchers to improve theories about the peopling of the Americas. In White Sands National Park, New Mexico, 60 human footprints have been astonishingly dated to around 22,000 years ago (Bennett et al. 2021). This date and location do not match either the Ice-Free Corridor or Coastal Route models. Researchers are now working to verify the find and adjust previous models to account for the new evidence. This groundbreaking find is sparking new theories; it is another example of the fast pace of research performed on our past.
Monte Verde is a landmark site that shows that the human population had expanded down the whole vertical stretch of the Americas to Chile by 14,600 years ago. The site has been excavated by archaeologist Tom D. Dillehay and his team (2015). The remains of nine distinct edible species of seaweed at the site shows familiarity with coastal resources and relates to the Coastal Route model by showing a connection between the inland people and the sea.
Named after the town in New Mexico, the Clovis stone-tool style is the first example of a widespread culture across much of North America, between 13,400 and 12,700 years ago (Miller, Holliday, and Bright 2013). Clovis points were fluted with two small projections, one on each end of the base, facing away from the head (Figure 13.19). The stone points found at this site match those found as far as the Canadian border and northern Mexico, and from the west coast to the east coast of the United States. Fourteen Clovis sites also contained the remains of mammoths or mastodons, suggesting that hunting megafauna with these points was an important part of life for the Clovis people. After the spread of the Clovis style, it diversified into several regional styles, keeping some of the Clovis form but also developing their own unique touches.
The Big Picture: The Assimilation Hypothesis
How do researchers make sense of all of these modern Homo sapiens discoveries that cover over 300,000 years of time and stretch across every continent except Antarctica? How was modern Homo sapiens related to archaic Homo sapiens?
The Assimilation hypothesis proposes that modern Homo sapiens evolved in Africa first and expanded out but also interbred with the archaic Homo sapiens they encountered outside Africa (Figure 13.20). This hypothesis is powerful since it explains why Africa has the oldest modern human fossils, why early modern humans found in Europe and Asia bear a resemblance to the regional archaics, and why traces of archaic DNA can be found in our genomes today (Dannemann and Racimo 2018; Reich et al. 2010; Reich et al. 2011; Slatkin and Racimo 2016; Smith et al. 2017; Wall and Yoshihara Caldeira Brandt 2016).
While researchers have produced a model that satisfies the data, there are still a lot of questions for paleoanthropologists to answer regarding our origins. What were the patterns of migration in each part of the world? Why did the archaic humans go extinct? In what ways did archaic and modern humans interact? The definitive explanation of how our species started and what our ancestors did is still out there to be found. You are now in a great place to welcome the next discovery about our distant past—maybe you’ll even contribute to our understanding as well.
The Chain Reaction of Agriculture
While it may be hard to imagine today, for most of our species’ existence we were nomadic: moving through the landscape without a singular home. Instead of a refrigerator or pantry stocked with food, we procured nutrition and other resources as needed based on what was available in the environment. This section gives an overview of how the foraging lifestyle enabled the expansion of our species and how the invention of a new way of life caused a chain reaction of cultural change.
The Foraging Tradition
There are a variety of possible subsistence strategies, or methods of finding sustenance and resources. To understand our species is to understand the subsistence strategy of foraging, or the search for resources in the environment. While most (but not all) humans today live in cultures that practice agriculture (whereby we greatly shape the environment to mass produce what we need), we have spent far more time as nomadic foragers than as settled agriculturalists. As such, it has been suggested that our traits have evolved to be primarily geared toward foraging. For instance, our efficient bipedalism allows persistence-hunting across long distances as well as movement from resource to resource.
How does human foraging, also known as hunting and gathering, work? Anthropologists have used all four fields to answer this question (see Ember n.d.). Typically, people formed bands, or kin-based groups of around 50 people or less (rarely over 100). A band’s organization would be egalitarian, with a flexible hierarchy based on an individual’s age, level of experience, and relationship with others. Everyone would have a general knowledge of the skills assigned to their gender roles, rather than specializing in different occupations. A band would be able to move from place to place in the environment, using knowledge of the area to forage (Figure 13.21). In varied environments—from savannas to tropical forests, deserts, coasts, and the Arctic circle—people found sustenance needed for survival.
Humans made extensive use of the foraging subsistence strategy, but this lifestyle did have limitations. The ease of foraging depended on the richness of the environment. Due to the lack of storage, resources had to be dependably found when needed. While a bountiful environment would require just a few hours of foraging a day and could lead to a focus on one location, the level and duration of labor increased greatly in poor or unreliable environments. Labor was also needed to process the acquired resources, which contributed to the foragers’ daily schedule (Crittenden and Schnorr 2017).
The adaptations to foraging found in modern Homo sapiens may explain why our species became so successful both within Africa and in the rapid expansion around the world. Overcoming the limitations, each generation at the edge of our species’s range would have found it beneficial to expand a little further, keeping contact with other bands but moving into unexplored territory where resources were more plentiful. The cumulative effect would have been the spread of modern Homo sapiens across continents and hemispheres.
Why Agriculture?
After hundreds of thousands of years of foraging, some groups of people around 12,000 years ago started to practice agriculture. This transition, called the Neolithic Revolution, occurred at the start of the Holocene epoch. While the reasons for this global change are still being investigated, two likely co-occurring causes are a growing human population and natural global climate change.
Overcrowding could have affected the success of foraging in the environment, leading to the development of a more productive subsistence strategy (Cohen 1977). Foraging works best with low population densities since each band needs a lot of space to support itself. If too many people occupy the same environment, they deplete the area faster. The high population could exceed the carrying capacity, or number of people a location can reliably support. Reaching carrying capacity on a global level due to growing population and limited areas of expansion would have been an increasingly pressing issue after the expansion through the major continents by 14,600 years ago.
A changing global climate immediately preceded the transition to agriculture, so researchers have also explored a connection between the two events. Since the Last Glacial Maximum of 23,000 years ago, the Earth slowly warmed. Then, from 13,000 to 11,700 years ago, the temperature in most of the Northern Hemisphere dropped suddenly in a phenomenon called the Younger Dryas. Glaciers returned in Europe, Asia, and North America. In Mesopotamia, which includes the Levant, the climate changed from warm and humid to cool and dry. The change would have occurred over decades, disrupting the usual nomadic patterns and subsistence of foragers around the world. The disruption to foragers due to the temperature shift could have been a factor in spurring a transition to agriculture. Researchers Gregory K. Dow and colleagues (2009) believe that foraging bands would have clustered in the new resource-rich places where people started to direct their labor to farming the limited area. After the Younger Dryas ended, people expanded out of the clusters with their agricultural knowledge (Figure 13.22).
The double threat of the limitation of human continental expansion and the sudden global climate change may have placed bands in peril as more populations outpaced their environment’s carrying capacity. Not only had a growing population led to increased competition with other bands, but environments worldwide had shifted to create more uncertainty. As such, it has been proposed that as people in different areas around the world faced this unpredictable situation, they became the independent inventors of agriculture.
Agriculture around the World
Due to global changes to the human experience starting from 12,000 years ago, it has been suggested that cultures with no knowledge of each other turned toward intensely farming their local resources (see Figure 13.22). It is proposed that the first farmers engaged in artificial selection of their domesticates to enhance useful traits over generations. The switch to agriculture took time and effort with no guarantee of success and constant challenges (e.g. fires, droughts, diseases, and pests). The regions with the most widespread impact in the face of these obstacles became the primary centers of agriculture (Figure 13.23; Fuller 2010):
- Mesopotamia: The Fertile Crescent from the Tigris and Euphrates rivers through the Levant was where bands started to domesticate plants and animals around 12,000 years ago. The connection between the development of agriculture and the Younger Dryas was especially strong here. Farmed crops included wheat, barley, peas, and lentils. This was also where cattle, pigs, sheep, and goats were domesticated.
- South and East Asia: Multiple regions across this land had varieties of rice, millet, and soybeans by 10,000 years ago. Pigs were farmed with no connection to Mesopotamia. Chickens were also originally from this region, bred for fighting first and food second.
- New Guinea: Agriculture started here 10,000 years ago. Bananas, sugarcane, and taro were native to this island. Sweet potatoes were brought back from voyages to South America around the year C.E. 1000. No known animal farming occurred here.
- Mesoamerica: Agriculture from Central Mexico to northern South America also occurred from 10,000 years ago; it was also only plant based. Maize was a crop bred from teosinte grass, which has become one of the global staples. Beans, squash, and avocados were also grown in this region.
- The Andes: Starting around 8,000 years ago, local domesticated plants started with squash but later included potatoes, tomatoes, beans, and quinoa. Maize was brought down from Mesoamerica. The main farm animals were llamas, alpacas, and guinea pigs.
- Sub-Saharan Africa: This region went through a change 5,000 years ago called the Bantu expansion. The Bantu agriculturalists were established in West Central Africa and then expanded south and east. Native varieties of rice, yams, millet, and sorghum were grown across this area. Cattle were also domesticated here.
- Eastern North America: This region was the last major independent agriculture center, from 4,000 years ago. Squash and sunflower are the produce from this region that are most known today, though sumpweed and pitseed goosefoot were also farmed. Hunting was still the main source of animal products.
By 5,000 years ago, our species was well within the Neolithic Revolution. Agriculturalists spread to neighboring parts of the world with their domesticates, further expanding the use of this subsistence strategy. From this point, the human species changed from being primarily foragers to primarily agriculturalists with skilled control of their environments. The planet changed from mostly unaffected by human presence to being greatly transformed by humans. The revolution took millennia, but it was a true revolution as our species’ lifestyle was dramatically reshaped.
Cultural Effects of Agriculture
The worldwide adoption of agriculture altered the course of human culture and history forever. The core change in human culture due to agriculture is the move toward not moving: rather than live a nomadic lifestyle, farmers had to remain in one area to tend to their crops and livestock. The term for living bound to a certain location is sedentarism. This led to new aspects of life that were uncommon among foragers: the construction of permanent shelters and agricultural infrastructure, such as fields and irrigation, plus the development of storage technology, such as pottery, to preserve extra resources in case of future instability.
The high productivity of successful agriculture sparked further changes (Smith 2009). It is argued that since successful agriculture produced a much greater amount of food and other resources per unit of land compared to foraging, the population growth rate skyrocketed. The surplus of a bountiful harvest also provided insurance for harder times, reducing the risk of famine. Changes happened to society as well. With a few farming households producing enough food to feed many others, other people could focus on other tasks. So began specialization into different occupations such as craftspeople, traders, religious figures, and artists, spurring innovation in these areas as people could now devote time and effort toward specific skills. These interdependent people would settle an area together for convenience. The growth of these settlements led to urbanization, the founding of cities that became the foci of human interaction (Figure 13.24).
The formation of cities led to new issues that sparked the growth of further specializations, called institutions. These are cultural constructs that exist beyond the individual and have wide control over a population. Leadership of these cities became hierarchical with different levels of rank and control. The stratification of society increased social inequality between those with more or less power over others. Under leadership, people built impressive monumental architecture, such as pyramids and palaces, that embodied the wealth and power of these early cities. Alliances could unite cities, forming the earliest states. In several regions of the world, state organization expanded into empires, wide-ranging political entities that covered a variety of cultures.
Urbanization brought new challenges as well. The concentration of sedentary peoples was ideal for infectious diseases to thrive since they could jump from person to person and even from livestock to person (Armelagos, Brown, and Turner 2005). While successful agriculture provided a large surplus of food to thwart famine, the food produced offered less diverse food sources than foragers’ diets (Cohen and Armelagos 1984; Cohen and Crane-Kramer 2007). This shift in nutrition caused other diseases to flourish among those who adopted farming, such as dental cavities and malocclusion (the misalignment of teeth caused by soft, agricultural diets). The need to extract “wisdom teeth” or third molars seen in agricultural cultures today stems from this misalignment between the environment our ancestors adapted to and our lifestyles today.
As the new disease trends show, the adoption of agriculture and the ensuing cultural changes were not entirely positive. It is also important to note that this is not an absolutely linear progression of human culture from simple to complex. In many cases, empires have collapsed and, in some cases, cities dispersed to low-density bands that rejected institutions. However, a global trend has emerged since the adoption of agriculture, wherein population and social inequality have increased, leading to the massive and influential nation-states of today.
The rise of states in Europe has a direct impact on many of this book’s topics. Science started as a European cultural practice by the upper class that became a standardized way to study the world. Education became an institution to provide a standardized path toward producing and gaining knowledge. The scientific study of human diversity, embroiled in the race concept that still haunts us today, was connected to the European slave trade and colonialism.
Also starting in Europe, the Industrial Revolution of the 19th century turned cities into centers of mass manufacturing and spurred the rapid development of inventions (Figure 13.25). In the technologically interconnected world of today, human society has reached a new level of complexity with globalization. In this system, goods are mass-produced and consumed in different parts of the world, weakening the reliance on local farms and factories. The imbalanced relationship between consumers and producers of goods further increases economic inequality.
As states based on agriculture and industry keep exerting influence on humanity today, there are people, like the Hadzabe of Tanzania, who continue to live a lifestyle centered on foraging. Due to the overwhelming force that agricultural societies exert, foragers today have been marginalized to live in the least habitable parts of the world—the areas that are not conducive to farming, such as tropical rainforests, deserts, and the Arctic (Headland et al. 1989). Foragers can no longer live in the abundant environments that humans would have enjoyed before the Neolithic Revolution. Interactions with agriculturalists are typically imbalanced, with trade and other exchanges heavily favoring the larger group. One of anthropology’s important roles today is to intelligently and humanely manage equitable interactions between people of different backgrounds and levels of influence.
Special Topic: Indigenous Land Management
Insight into the lives of past modern humans has evolved as researchers revise previous theories and establish new connections with Indigenous knowledge holders.
The outdated view of foraging held that people lived off of the land without leaving an impact on the environment. Accompanying this idea was anthropologist Marshall Sahlins’s (1968) proposal that foragers were the “original affluent society” since they were meeting basic needs and achieving satisfaction with less work hours than agriculturalists and city-dwellers. This view countered an earlier idea that foragers were always on the brink of starvation. Sahlins’s theory took hold in the public eye as an attractive counterpoint to our busy contemporary lives in which we strive to meet our endless wants.
A fruitful type of study involving researchers collaborating with Indigenous experts has found that foragers did not just live off the land with minimal effort nor were they barely surviving in unchanging environments. Instead, they shaped the landscape to their needs using labor and strategies that were more subtle than what European colonizers and subsequent researchers were used to seeing. Research from two regions shows the latest developments in understanding Indigenous land management.
In British Columbia, Canada, the bridging of scientific and Indigenous perspectives has shown that the forests of the region are not untouched wilderness but, rather, have been crafted by Indigenous peoples thousands of years ago. Forest gardens adjacent to archaeological sites show higher plant diversity than unmanaged places even after 150 years (Armstrong et al. 2021). On the coast, 3,500-year-old archaeological sites are evidence of constructed clam gardens, according to Indigenous experts (Lepofsky et al. 2015). Another project, in consultation with Elders of the T’exelc (William Lakes First Nation) in British Columbia, introduced researchers to explanations of how forests were managed before the practice was disrupted by European colonialism (Copes-Gerbitz et al. 2021). Careful management of controlled fires reduced the density of the forest to favor plants such as raspberries and allow easier movement through the landscape.
Similarly, the study of landscapes in Australia, in consultation with Aboriginal Australians today, shows that areas previously considered wilderness by scientists were actually the result of controlling fauna and fires. The presence of grasslands with adjacent forests were purposely constructed to attract kangaroos for hunting (Gammage 2008). People also managed other animal and insect life, from emus to caterpillars. In Tasmania, a shift from productive grassland to wildfire-prone rainforest occurred after Aboriginal Australian land management was replaced by British colonial rule (Fletcher, Hall, and Alexander 2021). The site of Budj Bim of the Gunditjmara people has archaeological features of aquaculture, or the farming of fish, that date back 6,600 years (McNiven et al. 2012; McNiven et al. 2015). These examples show that Indigenous knowledge of how to manipulate the environment may be invaluable at the state level, such as by creating an Aboriginal ranger program to guide modern land management.
The Future of Humanity
A common question stemming from understanding human evolution is: What will the genetic and biological traits of our species be hundreds of thousands of years in the future? When faced with this question, people tend to think of directional selection. Maybe our braincases will be even larger, resembling the large-headed and small-bodied aliens of science fiction (Figure 13.26). Or, our hands could be specialized for interacting with our touch-based technology with less risk of repetitive injury. These ideas do not stand up to scrutiny. Since natural selection is based on adaptations that increase reproductive success, any directional change must be due to a higher rate of producing successful offspring compared to other alleles. Larger brains and more agile fingers would be convenient to possess, but they do not translate into an increase in the underlying allele frequencies.
Scientists are hesitant to professionally speculate on the unknowable, and we will never know what is in store for our species one thousand or one million years from now, but there are two trends in human evolution that may carry on into the future: increased genetic variation and a reduction in regional differences.
Rather than a directional change, genetic variation in our species could expand. Our technology can protect us from extreme environments and pathogens, even if our biological traits are not tuned to handle these stressors. The rapid pace of technological advancement means that biological adaptations will become less and less relevant to reproductive success, so nonbeneficial genetic traits will be more likely to remain in the gene pool. Biological anthropologist Jay T. Stock (2008) views environmental stress as needing to defeat two layers of protection before affecting our genetics. The first layer is our cultural adaptations. Our technology and knowledge can reduce pressure on one’s genotype to be “just right” to pass to the next generation. The second defense is our flexible physiology, such as our acclimatory responses. Only stressors not handled by these powerful responses would then cause natural selection on our alleles. These shields are already substantial, and cultural adaptations will only keep increasing in strength.
The increasing ability to travel far from one’s home region means that there will be a mixing of genetic variation on a global level in the future of our species. In recent centuries, gene flow of people around the world has increased, creating admixture in populations that had been separated for tens of thousands of years. For skin color, this means that populations all around the world could exhibit the whole range of skin colors, rather than the current pattern of decreasing melanin pigment farther from the equator. The same trend of intermixing would apply to all other traits, such as blood types. While our genetics will become more varied, the variation will be more intermixed instead of regionally isolated.
Our distant descendants will not likely be dextrous ultraintellectuals; more likely, they will be a highly variable and mobile species supported by novel cultural adaptations that make up for any inherited biological limitations. Technology may even enable the editing of DNA directly, changing these trends. With the uncertainty of our future, these are just the best-educated guesses for now. Our future is open and will be shaped little by little by the environment, our actions, and the actions of our descendants.
Summary
Modern Homo sapiens is the species that took the hominin lifestyle the furthest to become the only living member of that lineage. The largest factor that allowed us to persist while other hominins went extinct was likely our advanced ability to culturally adapt to a wide variety of environments. Our species, with its skeletal and behavioral traits, was well-suited to be generalist-specialists who successfully foraged across most of the world’s environments. The biological basis of this adaptation was our reorganized brain that facilitated innovation in cultural adaptations and intelligence for leveraging our social ties and finding ways to acquire resources from the environment. As the brain’s ability increased, it shaped the skull by reducing the evolutionary pressure to have large teeth and robust cranial bones to produce the modern Homo sapiens face.
Our ability to be generalist-specialists is seen in the geographical range that modern Homo sapiens covered in 300,000 years. In Africa, our species formed from multiregional gene flow that loosely connected archaic humans across the continent. People then expanded out to the rest of the continental Eurasia and even further to the Americas.
For most of our species’s existence, foraging was the general subsistence strategy within which people specialized to culturally adapt to their local environment. With omnivorousness and mobility, people found ways to extract and process resources, shaping the environment in return. When resource uncertainty hit the species, people around the world focused on agriculture to have a firmer control of sustenance. The new strategy shifted human history toward exponential growth and innovation, leading to our high dependence on cultural adaptations today.
While a cohesive image of our species has formed in recent years, there is still much to learn about our past. The work of many driven researchers shows that there are amazing new discoveries made all the time that refine our knowledge of human evolution. Technological innovations such as DNA analysis enable scientists to approach lingering questions from new angles. The answers we get allow us to ask even more insightful questions that will lead us to the next revelation. Like the pink limestone strata at Jebel Irhoud, previous effort has taken us so far and you are now ready to see what the next layer of discovery holds.
Hominin Species Summary
|
Hominin |
Modern Homo sapiens |
|
Dates |
315,000 years ago to present |
|
Region(s) |
Starting in Africa, then expanding around the world |
|
Famous discoveries |
Cro-Magnon individuals, discovered 1868 in Dordogne, France. Otzi the Ice Man, discovered 1991 in the Alps between Austria and Italy. Kennewick man, discovered 1996 in Washington state. |
|
Brain size |
1400 cc average |
|
Dentition |
Extremely small with short cusps. |
|
Cranial features |
An extremely globular brain case and gracile features throughout the cranium. The mandibular symphysis forms a chin at the anterior-most point. |
|
Postcranial features |
Gracile skeleton adapted for efficient bipedal locomotion at the expense of the muscular strength of most other large primates. |
|
Culture |
Extremely extensive and varied culture with many spoken and written languages. Art is ubiquitous. Technology is broad in complexity and impact on the environment. |
|
Other |
The only living hominin. Chimpanzees and bonobos are the closest living relatives. |
Review Questions
- What are the skeletal and behavioral traits that define modern Homo sapiens? What are the evolutionary explanations for its presence?
- What are some creative ways that researchers have learned about the past by studying fossils and artifacts?
- How do the discoveries mentioned in “First Africa, Then the World” fit the Assimilation model?
- What is foraging? What adaptations do we have for this subsistence strategy? Could you train to be a skilled forager?
- What are aspects of your life that come from dependence on agriculture and its cultural effects? Where did the ingredients of your favorite foods originate from?
Key Terms
African multiregionalism: The idea that modern Homo sapiens evolved as a complex web of small regional populations with sporadic gene flow among them.
Agriculture: The mass production of resources through farming and domestication.
Aquaculture: The farming of fish using techniques such as trapping, channels, and artificial ponds.
Assimilation hypothesis: Current theory of modern human origins stating that the species evolved first in Africa and interbred with archaic humans of Europe and Asia.
Atlatl: A handheld spear thrower that increased the force of thrown projectiles.
Band: A small group of people living together as foragers.
Beringia: Ancient landmass that connected Siberia and Alaska. The ancestors of Indigenous Americans would have crossed this area to reach the Americas.
Carrying capacity: The amount of organisms that an environment can reliably support.
Coastal Route model: Theory that the first Paleoindians crossed to the Americas by following the southern coast of Beringia.
Early Modern Homo sapiens, Early Anatomically Modern Human: Terms used to refer to transitional fossils between archaic and modern Homo sapiens that have a mosaic of traits. Humans like ourselves, who mostly lack archaic traits, are referred to as Late Modern Homo sapiens and simply Anatomically Modern Humans.
Egalitarian: Human organization without strict ranks. Foraging societies tend to be more egalitarian than those based on other subsistence strategies.
Foraging: Lifestyle consisting of frequent movement through the landscape and acquiring resources with minimal storage capacity.
Generalist-specialist niche: The ability to survive in a variety of environments by developing local expertise. Evolution toward this niche may have been what allowed modern Homo sapiens to expand past the geographical range of other human species.
Globalization: A recent increase in the interconnectedness and interdependence of people that is facilitated with long-distance networks.
Globular: Having a rounded appearance. Increased globularity of the braincase is a trait of modern Homo sapiens.
Gracile: Having a smooth and slender quality; the opposite of robust.
Holocene: The epoch of the Cenozoic Era starting around 12,000 years ago and lasting arguably through the present.
Ice-Free Corridor model: Theory that the first Native Americans crossed to the Americas through a passage between glaciers.
Institutions: Long-lasting and influential cultural constructs. Examples include government, organized religion, academia, and the economy.
Last Glacial Maximum: The time 23,000 years ago when the most recent ice age was the most intense.
Later Stone Age: Time period following the Middle Stone Age with a diversification in tool types, starting around 50,000 years ago.
Levant: The eastern coast of the Mediterranean. The site of early modern human expansion from Africa and later one of the centers of agriculture.
Megafauna: Large ancient animals that may have been hunted to extinction by people around the world.
Mental eminence: The chin on the mandible of modern H. sapiens. One of the defining traits of our species.
Microlith: Small stone tool found in the Later Stone Age; also called a bladelet.
Middle Stone Age: Time period known for Mousterian lithics that connects African archaic to modern Homo sapiens.
Monumental architecture: Large and labor-intensive constructions that signify the power of the elite in a sedentary society. A common type is the pyramid, a raised crafted structure topped with a point or platform.
Mosaic: Composed from a mix or composite of traits.
Neolithic Revolution: Time of rapid change to human cultures due to the invention of agriculture, starting around 12,000 years ago.
Ochre: Iron-based mineral pigment that can be a variety of yellows, reds, and browns. Used by modern human cultures worldwide since at least 80,000 years ago.
Sahul: Ancient landmass connecting New Guinea and Australia.
Sedentarism: Lifestyle based on having a stable home area; the opposite of nomadism.
Southern Dispersal model: Theory that modern H. sapiens expanded from East Africa by crossing the Red Sea and following the coast east across Asia.
Subsistence strategy: The method an organism uses to find nourishment and other resources.
Sunda: Ancient Asian landmass that incorporated modern Southeast Asia.
Supraorbital torus: The bony brow ridge across the top of the eye orbits on many hominin crania.
Upper Paleolithic: Time period considered synonymous with the Later Stone Age.
Urbanization: The increase of population density as people settled together in cities.
Wallacea: Archipelago southeast of Sunda with different biodiversity than Asia.
Younger Dryas: The rapid change in global climate—notably a cooling of the Northern Hemisphere—13,000 years ago.
For Further Exploration
Websites
First-person virtual tour of Lascaux cave with annotated cave art: Ministère de la Culture and Musée d’Archéologie Nationale. “Visit the cave” Lascaux website.
Online anthropology magazine articles related to paleoanthropology and human evolution: SAPIENS. “Evolution.” SAPIENS website.
Various presentations of information about hominin evolution: Smithsonian Institution. “What does it mean to be human?” Smithsonian National Museum of Natural History website.
Magazine-style articles on archaeology and paleoanthropology: ThoughtCo. “Archaeology.” ThoughtCo. Website.
Database of comparisons across hominins and primates: University of California, San Diego. “MOCA Domains.” Center for Academic Research & Training in Anthropogeny website.
Books
Engaging book that covers human-made changes to the environment with industrialization and globalization: Kolbert, Elizabeth. 2014. The Sixth Extinction: An Unnatural History. New York: Bloomsbury.
Overview of what human life was like among the environmental shifts of the Ice Age: Woodward, Jamie. 2014. The Ice Age: A Very Short Introduction. Oxford: OUP Press.
Articles
Recent review paper about the current state of paleoanthropology research: Stringer, C. 2016. “The Origin and Evolution of Homo sapiens.” Philosophical Transactions of the Royal Society B 371 (1698).
Overview of the history of American paleoanthropology and the many debates that have occurred over the years: Trinkaus, E. 2018. “One Hundred Years of Paleoanthropology: An American Perspective.” American Journal of Physical Anthropology 165 (4): 638–651.
Amazing magazine article that synthesizes hominin evolution and why it is important to study this subject: Wheelwright, Jeff. 2015. “Days of Dysevolution.” Discover 36 (4): 33–39.
Fascinating research on Ötzi, a mummy from 5,000 years ago: Wierer, Ursula, Simona Arrighi, Stefano Bertola, Günther Kaufmann, Benno Baumgarten, Annaluisa Pedrotti, Patrizia Pernter, and Jacques Pelegrin. 2018. “The Iceman’s Lithic Toolkit: Raw Material, Technology, Typology and Use.” PLOS One 13 (6): e0198292. https://doi.org/10.1371/journal.pone.0198292.
Documentaries
PBS NOVA series covering the expansion of modern Homo sapiens and interbreeding with archaic humans: Brown, Nicholas, dir. 2015. First Peoples. Edmonton: Wall to Wall Television. Amazon Prime Video.
PBS NOVA special featuring the footprints found in White Sands National Park: Falk, Bella, dir. 2016. Ice Age Footprints. Boston: Windfall Films. https://www.pbs.org/wgbh/nova/video/ice-age-footprints/.
PBS NOVA special about how modern humans evolved adaptations to different environments. Shows how present-day people live around the world: Thompson, Niobe, dir. 2016. Great Human Odyssey. Edmonton: Clearwater Documentary. https://www.pbs.org/wgbh/nova/evolution/great-human-odyssey.html.
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Acknowledgments
I could not have undertaken this project without the help of many who got me to where I am today. I extend sincere thank yous to the many colleagues and former students who have inspired me to keep learning and talking about anthropology. Thank you also to all who are involved in this textbook project. The anonymous reviewers truly sparked improvements to the chapter. Lastly, the staff of Starbucks #5772 also contributed immensely to this text.
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